Session 29 – Photo Replication on Ceramics

Laser Engraving Ceramics

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The Concise RDWorks Learning Lab with Russ Sadler. Session 29- Photo replication with ceramics.

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Well, today we’re going to go one step higher on the photo replication ladder.

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This is the top of the tree. Look what we have here a ceramic tile, a white ceramic tile.

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We’ll not on this site, but on this side a picture that you’re all familiar with.

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But just take a look at the quality of that.

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Now, that process was discovered by a guy called Nikki Norton, now he discovered this process while using a very short wavelength laser.

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It’s a basically a blue diode laser at very low power, maybe five or 10 watts.

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Now it isn’t just a simple matter of engraving on the surface of the white tile like we did when we did this on slate.

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It isn’t very difficult to do, but the process itself is scientifically very complex.

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He discovered that if you paint white paint onto a white tile.

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And then engrave something. When you remove the white paint, what you’re left behind is a black,

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completely indelible image that’s burned into the surface of the tile.

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I use that word burnt very loosely. If you want to understand how the paint process works.

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Go and have a look anywhere on YouTube and just put in ceramic tile engraving or something like that.

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And you will find all sorts of videos, people telling you how to do it.

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They won’t give any credit to Nikki Norton, who’s the guy that discovered the process,

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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but somebody wanted to upgrade from a blue laser machine up to a CO2 laser machine.

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And they asked me the question very simply, does this process work at 10600 nanometres,

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i.e. ten point six micron wavelength, which is where we operate.

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I had no idea. So I had to do a lot of research and experimentation to find out how to do it.

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Now, basically what I’ve done, I’ve cut out the middleman, i.e. the paint,

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and I’ve gone straight to the real thing that causes this process to happen, which is a material called titanium oxide.

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It’s a white pigment that’s used widely in the paint industry.

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It’s also used as a food colouring in toothpaste and various other things.

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It’s a very interesting subject light, as we’ve already discovered, because we’re using light to make our laser machine work.

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Light energy through a lens focuses it down, makes it very intense, shakes the molecules and they destroy themselves.

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They shake themselves to death and change from one one chemical to another. Here we are.

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We’re starting off with white. We’re doing something to it and we’re making it black.

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But we’re not burning it. So what’s going on?

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How can we make white black?

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Remember, we touched on the subject in the last session when we made black acrylic turn white, and that was all to do with the trick of the light.

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Light, has got a lot to answer for. There’s a lot of science in light, so really today what we’re going to do,

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I’m going to show you how this process works and understand the science behind how it works,

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and you’ll be amazed at the quality of work you can produce on a white tile.

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Because yes, it does work with the CO2 laser and I’ve decoded how it works.

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I will reveal that secret to you as we go through some science. Oh not more science.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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And as I’ve told you many times before, this whole subject of laser is touching onto all aspects of physics,

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mainly light and the interaction of light with molecules in materials.

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So let’s quickly go through in the next few minutes the basic science of light, colour, what you see and what light is.

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We touched on the electromagnetic spectrum in the early days when we tried to focus in on where our ten point

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six micron wavelength was in the overall thing that’s all around us called the electromagnetic spectrum.

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But let’s just have a quick refresher OK, we will come at this subject quite gently from a from a point of view of things that you already know,

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I’m sure you understand how sound waves work.

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So these pulses of energy hit your eardrum and make it vibrate 20 cycles, a second up to about 20000 cycles a second.

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Now that typically is the range of frequency that you can hear.

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Look, these are still waves, but this time they are light waves, not sound waves.

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Now this is something called an electromagnetic spectrum because these are electromagnetic waves.

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Now they do the same thing as sound waves. They hit things and then make them vibrate.

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We’ve got a range that we can see in this spectrum it’s this colour range.

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All the colours of the rainbow. That’s because we’ve got sensors in the back of our eye, which are only sensitive to this range of frequencies.

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Outside this range of frequencies, we cannot see what’s happening elsewhere.

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We can’t see X-rays, we can’t see microwaves, we can’t see phone signals or radio waves or TV signals. Our audible hearing is 20000 cycles a second.

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And yet here we are at over a trillion cycles a second.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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And that’s what our eyes are capable of perceiving. Look.

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I’ve got a handful of light here. I’ve got all sorts of frequencies of light waves in my hand.

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What colour is it? Hmm, interesting problem.

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What is light? Well, it’s it’s this stuff that’s around us.

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It’s here. It’s here, it’s everywhere. What colour is that?

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I’ve just shown you that the only colors the eyes can perceive these colors of the rainbow here.

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Is there any white? In that colour spectrum.

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No. So how come you can see that?

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Well, the answer is very simple. White light

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is a combination of all the colours of the rainbow, every single colour of the rainbow is being reflected off that surface.

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Now I’ve probably done this before, but I’ll give you this example again. We’ve got a stone that’s falling from the sky.

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Is it dangerous? No. Not until,

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it hits you on the head. And at the instant it hits you on the head, it gives up the energy that it has and you can feel it, something happens.

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Well, that’s exactly what happens with light. It’s traveling through space forever and ever and ever until he hits something,

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and when it hits something solid and it’s not gas when it hits something solid.

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It gives up its energy just like the stone hitting your head, and something happens and the something that happens depends on the material that it hits.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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Now in this instance, what’s happening is the light energy is passing through that paper and traveling on forever and ever and ever except.

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That small part there, which our eyes are sensitive to.

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And at that frequency, those wavelengths are being reflected off of the surface of this material.

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The whole range of the colour of the rainbow. To create the impression of white light, there is no white.

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White is a combination of all these colours that we perceive in our brain through our eyes.

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What’s the difference between that and this?

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All the colours of the rainbow are hitting this, and you see white light, all the colours of the rainbow hitting this, and you see a mauve light.

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Why? Well. When the light hits this surface, it’s a mirror.

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It all reflects. And you see the combination of all of those colours.

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That you imagine to be white?

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When the colours of the rainbow, this surface, the pigment, or whatever it is that’s in this material here absorbs most of the colors of the rainbow.

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And the only ones that are reflected are the ones that make pink or mauve light.

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So we see colour. By. Absorption of light, only those colours that are reflected.

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Are we perceiving. Here, we perceive all of them here, we perceive just some of them.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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Okay, so what colour is that? Yeah, I know it’s black.

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But what is black? The light is hitting that because it’s not passing through for ever and ever and ever.

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How much of it is reflected to your eyes? Is there any black in the colours of the rainbow?

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No, in the same way that there’s no white, this is total absorption of the light energy that’s hitting the surface.

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There is no light being reflected and you just see it is a colour that you imagine to be black.

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So as I said, light is a very funny thing. It’s a fascinating subject.

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We’re going to go back to this thing again that I demonstrated to you on a previous occasion.

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This is my jar of water with a little bit of soap in it.

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What’s happening to the light there? Look. It’s passing right through this.

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It’s not being reflected to my eyes. It’s no colour.

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It’s transparent. I can see right through it.

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OK, because the only time that something is happening is when the light hits my hand behind there and you can see my hand.

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Until then, it’s basically transparent and the light is passing through it.

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But when I do this, it turns white.

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As I explained to you in the previous session, it only turns white because the light is being absorbed and reflected off of those bubbles.

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So white is a perception and black is a perception?

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Black is absence of colour, and white is full reflection of all the colours of the rainbow.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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I want you to bear that in mind because when you see colour, you must see it as some sort of chemical change,

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which is changing the absorption characteristic of this stuff because of a strange mix of absorption or reflection of these things here,

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the colours of the rainbow. And that brings us back nicely to this subject here.

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Nikki Naughton painted white paint onto a white surface.

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Hit it with a laser beam, took the paint off and found that what he got behind, it was a completely indelible image.

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How did White turn into black? And that’s what we’re going to just investigate now,

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what I’ve got here is my titanium oxide that I used for engraving on a white tile. In that instance,

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what we have is a white powder, very, very finely ground white powder that started off life like a piece of coal – black.

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And remember, what I’ve just said to you, black is total absorption of all the light, it’s not transmitting any back at you.

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And white is reflecting all of the light back at you. So somewhere between when this was originally made and what they’ve done to it now,

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which is turn it into a very, very, very fine powder, the crystal structure of that material has changed.

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So that it has got different light absorption properties.

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It’s still the same material. Basically, that is still a black material.

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But black is not a colour any more than white is a colour. They just happen to be different ways of reflecting the light.

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I’m going to have a go at burning that with the laser beam. We’re going to see what happens.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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I don’t know what’s going to happen. I know what happens when I paint it onto a white tile and I heat it up.

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It turns black because what it does, it starts to recombine all these microparticles that are in here.

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Back to what it was originally like a piece of coal. This requires a very high temperature to make it turn into something else.

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But whether we should be able to achieve that, I don’t know. OK.

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So what have we got here? Look, we’ve got a piece of coal from white material.

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We’ve turned it back to what it was originally black material.

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And that is how the Nikki Naughton process works.

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And I bought some white tiles and some titanium dioxide, which I tried to apply in various ways last time,

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very crudely with a brush using a small amount of isopropyl alcohol to turn it into a creamy mixture.

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I quickly realized that the variation in the surface texture was going to absorb the light energy in different ways and produce different net results.

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One of the techniques I tried is to mix up a suspension in water and tried applying it with a just an ordinary plant spray bottle.

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The idea was very simple and logical. The suspended particles sitting in this lovely, smooth,

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fluid film would drop down onto the surface and produce an even layer of sediment on the surface.

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The sediment has actually migrated away because of the surface tension on the glaze underneath.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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And I bought myself an airbrush, not something I’ve ever used before.

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Very conveniently mark this little bottle here with three marks.

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One third of it has been filled up with the titanium dioxide, and I’m now going to fill it up to probably two thirds full.

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That’s my starting mixture.

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Who knows whether or not it’s the right mix, so we just give that a jolly good mix to try and break down all the particles into very fine suspension.

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And we’ll clean two or three tiles with some acetone. Make sure we got that nicely suspended with a final shake.

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So I’ve now changed the mix to one part titanium dioxide and three parts isopropyl alcohol to make it a thinner,

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mix. Just two or three minutes and you can see how quickly

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this has sedimented out. There’s the clear liquid and it’s still busy settling down.

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But to be honest, the really interesting and major part of this exercise has been trying to decode how we turn white titanium dioxide black.

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And that all comes down to heat changing the crystal structure.

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So I feel very confident about that. And from the quick tests that I did on my tile, the teeny weeny bit of tile.

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I know that it’s going to make a black mark, but it had a little black mark in the middle.

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And then around the outside of that black mark, we had a melt pool of glaze. To do photo engraving.

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What I call proper photo engraving requires precision dots, and I’m not sure that I’m going to get precision dots off CO2.

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I’ve never seen any physical work from the diode laser.

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I’ve seen photographs of pictures that look pretty good.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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But I don’t know exactly how good they are.

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Now I understand that most people that are using diode lasers, use an image conversion program of free or low

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cost called ImagR. OK, now I’d like you to join me with a bit of an examination of this image that’s on the screen.

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Question one. What is it? I don’t mean a young female savage?

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I mean, this is a drawing. Is it a painting?

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Is it a photograph. I don’t think anybody will ever mistake that for a photograph?

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And artistic impression of some sort. I mean, just take a look here.

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What’s this? Is this hair or is this straw?

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Let’s have a quick look here. What are all these marks here?

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Is this a sign of a very old lady with wrinkles on her skin?

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Could be because look at these lips. Those are the lips of a 70 year old.

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But that face is the face of a 20, 25 year old young lady who’s had a bad makeup day.

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Is this war paint? Or is this actually cut in scars?

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These look very much as though they’re deep scars in her cheek.

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These are just a few of the minor details I’m pointing out to you on this picture.

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If an artist had drawn this, he wouldn’t have put these wrinkles in here because those wrinkles don’t belong there.

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They’re not even shadows of these pieces of hay, straw, hair, call it whatever you like.

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Look at this bright white line down here. Where does that come from?

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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Has she got some sort of light behind her chin? Everything about this picture says there’s something wrong and it is a very, very nice photograph.

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And you can clearly see that it is a 22 to 25 year old young lady.

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That’s got beautiful hair. She hasn’t really got deeply cut wrinkles in her lips.

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She hasn’t even got scars on her face. Look at those moody eyes.

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They’re not the same starey eyes that you’re seeing here. So what’s the difference between these two?

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How has that photograph been so badly distorted into this?

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Cartoon? Pencil sketch, I don’t know how to describe it.

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Now this is a sort of photo preparation work that’s carried out by let’s call them the big boys.

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There are a couple of pieces of commercial software that you can buy. I think one is called “one touch”, and the other I think is called “photograf”.

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They belong to two large companies that are selling RF laser machines.

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Now, as I commented to you a little bit earlier, the RF laser machine that I’ve got.

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It’s absolutely rubbish at producing photo quality engraving.

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And so consequently, to overcome the problem of not being able to produce photo quality engraving.

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They produced distorted images that take into account the weaknesses of the photo engraving process that they can carry out on these machines.

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Now, this is not from one of those two big companies.

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This is an example from the software that probably you guys are using.

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It’s called ImagR. Look how light this is in relation to the original.

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Look how little grey, there is in here.

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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It’s been stripped of most of its shades.

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It’s been sharpened to death. To turn her hair into straw.

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Yes. They’re similar. They’re the same, but they’re not the same.

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Now what I want to do is to describe to you why this

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has arrived from that. You are not going to produce this when you put your image has been prepared for laser engraving down onto a piece of material.

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You will get something like this. You will not get anything like this.

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Now, to me, that is not photo engraving.

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And I hope I’m going to be able to demonstrate to you with this technique that Nikki has developed of black dots on a white tile.

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Something I’ve been trying to achieve for a long time since the few laser tiles that I managed to acquire, slipped through my fingers.

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When I had those laser tiles, I was getting close to this sort of quality on a laser tile.

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Now if you’ve never come across dithering before you’ll see what it is in a minute. There are various choices here in Photoshop for different sorts of dithers?

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Stick with the diffusion dither because for laser work, this is the best.

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Let’s just do it. There we go, we’ve done it. We’ve now turned that picture into a binary image.

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This picture is stored in memory and the software scans across backwards and forwards,

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and as it scans across backwards and forwards, it reads these dots like Morse code.

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So let’s just take a look. Just here, we’ve got a line of about four or five pixels.

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Then we’ve got a gap of two. Then we’ve got a single pixel, gap of two, single pixel, gap of two, single pixel.

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And so it runs across here. And then look, here we’ve got black pixel white pixel black pixel, white pixel. To help us set the machine,

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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if you can reproduce this pattern, which is 254 PPI pattern.

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And this is the pattern that I use for calibrating and setting my machine.

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If you can achieve this pattern cleanly and clearly, then you have the capability of copying these individual pixels on here,

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which are point one, so photo replication is an exact copy of these pixels.

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If the dot that you produce is bigger than these pixels, then the ratio of black and white in this image will change.

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And the picture will get darker because the dots are bigger and the amount of white in the picture becomes less.

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And your eye will see it as a darker picture. That’s the basic principle, as I said, of how dithering works to fool your eye.

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You saw me use this pattern in the last video when I was trying to establish the correct power and speed to run at.

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So having carried out this pattern already, I know that I can get pretty good dots on the CO2 laser machine,

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which gives me a great deal of hope that I shall be able to achieve,

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reasonable quality photo replication. Remember what the rule of photo replication is?

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One pixel must be copied by one dot. The same size dot as the pixel. Pixels do not overlap, therefore, dots must not overlap.

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There’s only two colours in that picture black and white.

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You have got control of the black, and indirectly you will control the white by going smaller or larger with your black.

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So it’s important that you control the size of the black dot that you’re going to put down. If you can copy every black dot,

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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then you will replicate that picture without any need for this distortion software.

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The only thing that you need is a good dithering algorithm and as I said, Floyd Steinberg is it.

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Now we can see in this picture how many single pixels we’ve got, they’re all over the place.

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Because those are the things that are providing gentle shades of gray.

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So let’s go and have a look at the other image which has been sitting over there quietly beside us.

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And now we can look at that image and we can see. Hang on. We’ve got virtually no black pixels on there. And

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if we had,

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overlap at the end of each one of those pixels, there is so much white in there that it would do virtually no damage to the ratio of black and white.

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And that’s the essence of why these pictures are so distorted.

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You’re trying to remove the single pixels away and you’ll notice a lot of these pixels in here are all joined up black pixels.

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There’s not many single pixels. There are some single pixels in here.

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But you know, they will have to just come in and get slightly darker.

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So the whole picture has been lightened. So that it allows for these picture pixels to make the picture darker in places.

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It’s a trick that’s used to try and make the image look more like the original.

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But it never will be a photo replication. That’s the sort of picture I’ve been getting when I’ve been doing these little dot tests down here.

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So there’s the image I’m going to try and reproduce because it tells me a great deal about the dot quality that I’m going to be able to achieve.

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As you can see, this is a this is a dithered pattern, 254 dots per inch.

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But the sort of things that we’re looking for in the end result are the resolution of the nostrils and the colour in the eyes.

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Okay. I’m very confident I should be able to pick up all these hairs that are on here.

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That’s not a problem. And these whiskers, they’ll come out. But it’s really the density of the blacks,

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that’s more important. Whether we can pick up these different density of blacks. We see that it’s got a lot of black in it and not much white.

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And here you’ve got just a few whites.

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So if these black dots are too big, they will merge into each other and they will, if you like swamp the white that’s supposed to be in there.

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So it’s most important that what I’m doing with this image is to produce one dot,

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equals one pixel, and the pixels are 0.1 square. So I’m looking to produce a 0.1 round dot to get as close as I can to this picture.

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And that’s the aim of photo engraving. As far as I’m concerned, one dot equals one pixel.

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Now I’ve set the power quite high at 40 per cent.

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Which is about 3~35 watts.

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But I’m running at 400mm a second.

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So the exposure time for each dot is very small.

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There’s the final result before I wash any of the titanium dioxide off. That’s what

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It’s like when the titanium dioxide has been washed off, literally it was just washed off under water.

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No solvent or anything required? And let’s just zoom in and have a bit of a look at the detail we’ve managed to get on this picture.

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Remember, I was worried about the eyes. They’ve come out extremely well.

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Look we’ve managed to get all those hair details in the ear. And all those very minor hairs down the side of the face, those lovely whiskers.

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And I have to say that, to be honest, it’s probably one of the best versions of that picture I’ve ever managed to create.

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It looks as though we’ve managed to get the pixels and the dots matching. Now,

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although these dots are exactly like those that I produced during my test.

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It’s amazing that they come out as well as they do.

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We know that the relationship between these is naught point one.

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So using that as a scaling reference, we can see that that dot there is about point one.

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The melt zone is more than point one. The dot is less than point one.

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And these dots are less than point one as well, wide, because if they were point one, they would touch each other.

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I don’t know how the colour of this glaze affects the final presentation.

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The glaze is approximately naught. Point one. But the dots in the centre are roughly 0.05, as you can see.

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So does that mean to say possibly I could force this picture to something like about a 508 resolution, five hundred dots per inch?

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These little blobs of glaze that have melted around the titanium dioxide are rather interesting. I don’t know whether

Transcript for Photo Replication and Laser Engraving Ceramics (Cont…)

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they’re going to act like little magnifying glasses and somehow spread the black dot out for our visual observation.

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So we’ve got the edge of the melt and the titanium dioxide roughly on the same plane.

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We’re just coming into focus with the tile itself. This melt has raised by roughly two or three microns above the surface of the tile.

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This black blob that we’ve created has sunk into the molten glass or the molten glaze material.

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Okay. And it’s sitting virtually level with the surface of the tile.

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But it is interesting to note that right around the outside of all of these look, we’ve got a little encrustation of titanium dioxide.

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The white titanium dioxide. It could well be that that is actually never going to come off

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because it somehow just in a transition phase where it’s starting to clump together,

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but it hasn’t yet had enough temperature to turn it black. Now this has been a very,

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very interesting session for me because despite the fact that I said earlier on that my

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main interest in this subject was trying to decode how the titanium oxide turns black.

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Now that it has turned black and I’ve seen the results. It’s absolutely fascinating.

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I’m interested in the science and the technology or methodology of how we get to a quality picture like this.

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Now this is the best quality picture that I’ve ever produced. Because of the great contrast between the white background and the black dots,

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this is coming close to the process that we’ve all hijacked from the print industry.

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This dithering technique was never intended for laser machines,

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but it just so happens that now we have the ability to produce precision black dots on a superb white background.

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We’re back to exactly what the print industry designed this technology for.

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Well. A very successful session. And a few days later, I pushed it to 508 dpi, double the resolution.

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Enjoy this last bit.

Transcript for Photo Replication and Laser Engraving Ceramics