Session 07 – Laser Beam Safety

The Concise RDWorks Learning Lab Series

Welcome to the new Concise RDWorks Learning Lab Series with Russ Sadler. In this session, Russ explains the real life risks associated with using a laser machine, to assist you in determining your own laser machine risk analysis and especially laser beam safety.

Over the last 6 years, Russ has built up a formidable YouTube following for his RDWorks Learning Lab series which currently has over 200 videos.

The original RDWorks Learning Lab series on his “Sarbar Multimedia” YouTube Channel, follows Russ as he tries to make sense of his new Chinese laser machine and to sort out the truths, half truths and outright misleading information that is available on the web.

Six years later with over 4 million YouTube Views under his belt, Russ has become the go to resource for everything related to the Chinese CO2 laser machine user or wannabe user.

Laser Beam Safety - A working Tube
Laser Beam Safety – A working Tube

In this new series, Russ has condensed his knowledge and experience of the last 6 years to provide valuable information and insights into the purchasing, understanding, use, repair and maintenance of the Chinese CO2 laser machines and their key component parts.

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Transcript for Laser Beam Safety

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The Concise RDWorks Learning Lab with Russ Sadler. Session 7: Laser Beam Safety.

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Well, it’s six years since I bought my first laser machine,

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and we’re at a point now in this short series where we’re going to talk about laser safety.

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Now, remember, I said I’ve been using these machines for six years. Am I dead?

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Am I blind? I know I’m ugly and gray, and fact, and old, but that’s just something that God has given me.

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It’s not self-inflicted. I want to talk today about the safety aspects of this laser machine and particularly the laser beam itself.

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Now, I have another series running which documents my six years of learning with this machine.

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It’s a bit like watching grass grow, so it’s not for the faint hearted.

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And it’s called RDWorks Learning Lab. Just recently I did a video about laser safety.

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And so I’m not going to bother to remake that video.

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So what we’re going to do now is let my cardboard clone take you through the next part of this safety session.

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Well, welcome to this unplanned session of RDWorks Learning Lab, now two things.

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First of all, unplanned. Every session I do is unplanned.

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But what I really mean is this was not intended to be part of the sequence of my thought processes.

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As far as RDWorks Learning Lab is concerned, we’re in the middle of doing something with lenses at the moment.

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And hey, this is just a major interruption, but. Oh, what do you mean?

Transcript for Laser Beam Safety (Cont…)

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I’ve got a screw loose. Yeah, I know that. that’s what happens when you buy cheap Pound Shop glasses. But,

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I am wearing these for very good reason. And will go on to explain that in a minute.

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Today, this unplanned session is all about laser safety.

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Now I know you see me using this machine all the time, you think, without glasses on.

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But of course, out of camera. I’ve always got my my reading glasses on.

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Yeah, there’s another very expensive pair of glasses there as well. Newcomers to this hobby are continuously asking me when they see my videos.

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Why are you working the machine with the lid open? Surely, that’s dangerous?

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What sort of safety glasses can you recommend that I buy?

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I’ve seen you can get safety glasses from sort of something like about twenty dollars up to maybe two hundred dollars, which are the best ones to buy.

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Well, I hope by the end of this session you won’t need to ask me those questions.

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I’m not just going to give you a quick, glib answer which says, yes, this machine is safe or this machine is not safe.

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Therefore, you know, you need all your earmuffs and your eyeglasses and all the rest of the gear on.

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You need to understand how dangerous this machine is, so that you can make your own assessment.

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Fear of the unknown gives the opportunity for those people that want to sell you 200 pound glasses a great opportunity.

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They’re preying on your fear. Now you can make up your own mind about the risks after you watch this video.

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So let’s dive in and we’ll start off at the beginning.

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Now, I’m going to go into some of the physics behind the laser technology.

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Don’t get too concerned because this is not anything complicated that requires a master’s degree or anything like that.

Transcript for Laser Beam Safety (Cont…)

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But I’m only going to give you a few basic facts enough for you to build a picture and assess what the safety issues are.

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OK, here we are looking at the laser tube and it’s just about to switch on.

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And there we go. And if you listen carefully, you’ll hear something going on at the front of the machine, which I’ll explain in a minute.

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But what you see there in the laser tube is a pink beam.

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Now that pink beam is not and I repeat not the laser, that is just basically lightning in a bottle. That’s ionized nitrogen,

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which is part of the chemistry that creates a laser beam.

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Now what’s coming out of the end just here where my finger is.

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This brass thing, is the laser beam. It’s invisible.

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If that pink beam was the laser beam, then you’d expect to see a pink beam around the front of the machine.

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But you can’t, because the laser beam is invisible.

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OK, so this beam bounces off mirrors.

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Here’s one of them here.

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So over here, we’ve got a second mirror where the beam bounces off of and then there’s another mirror and that directs the beam down. In here,

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you’ve got a lens made of this strange yellow material.

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And that lens does exactly the same as a magnifying glass.

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It amplifies the laser beam into something that is very, very, very dangerous as opposed to just dangerous.

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Laser beams have got different classifications.

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The silly thing is this machine has got all these labels on it and it says it’s a Class 1 laser product.

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Ha ha. No, it’s not. It’s only a class one laser product.

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If you keep the lid closed. When you look at this specification. Class 1 says

Transcript for Laser Beam Safety (Cont…)

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It’s safe for viewing directly with the naked eye. Well, provided we got the lid down, that is true.

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In reality, it’s a Class 4 product and a Class 4 says;

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This is the highest class of laser radiation. Radiation in this class is very dangerous.

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And viewing of the diffused reflection may be dangerous.

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It says may. Class 4 laser beams are capable of setting fire to materials onto which they are projected.

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There we go, now the laser beam is running. Can you see a laser beam across there?

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You can’t because I told you it’s invisible. But trust me, it is there.

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And what did it do? It set fire to things. So this is a Class 4 laser, and on that basis, everybody’s going to try and sell you safety equipment.

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I will explain what’s going on here in a little while. But at the moment, you can see I’m trying to boil myself up some water for a new cup of coffee.

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OK, so you’re watching this because you’re a newcomer to the hobby.

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Now, old timers will know and they will recognize my colored pins and this piece of paper.

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I’m pretty good at dodgy diagrams. And as I’ve commented many times, I always remember my art teacher at school telling me, take up plumbing boy.

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There are a few pieces of basic science associated with laser cutting, laser engraving, the laser beam.

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The first thing is, it’s a beam of light. It’s not a beam of heat, which many people seem to be confused by.

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Now, you’ll recognize this as a wave.

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Now, if this was sound, you could hear it and it would go on your ear drums and it would make them do this vibrate.

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That would be a frequency of round about anything from five to maybe 20000 cycles

Transcript for Laser Beam Safety (Cont…)

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a second. Light is exactly like this, but it’s in a different league. Instead of 20000 cycles

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a second maximum, which is what you can hear when you’re young. We’re talking about a thousand billion cycles per second,

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a completely different league of frequency. Now whether they’re sound vibrations or light vibrations, at a completely different frequency makes no difference.

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Let me give you a silly example of what I’m going to start to talk about.

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If we have a table and we put a jelly or jello, depends on which part of the world you’re from, on the table.

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You know, the sort of thing you have at birthday parties and a cake. And then you grab hold of the table and you start shaking it.

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What happens? You shake it at a certain frequency and the jelly goes bonkers.

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What does the cake do? Nothing, the reason being the material structure itself is completely different.

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The jelly responds to your shaking and the cake doesn’t. Now,

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if you shake the table fast enough and hard enough, you will have an effect on the cake as well.

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But the cake responds at a different frequency. So there is a very good example of two different materials.

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Different materials react differently to frequencies.

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Now, everything in this world, my pens, the paper, the metal, everything that you can see around me,

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including your skin, is made up of molecules and atoms and all atoms and molecules are always doing this.

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They’re vibrating. They’re shaking.

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Now, it’s a physics principle that they don’t teach you about at school because it’s too complex for young kids to think about.

Transcript for Laser Beam Safety (Cont…)

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The vibration level of a molecule is its temperature, the more it vibrates, the hotter it is.

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And that’s what temperature is, the amount of vibration in a molecule or atom.

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Let’s turn this whole thing around again and come back to these frequencies and our jelly and our cake, which is material.

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And even they are shaking like this. But of course, light at several thousand billion cycles a second, which is totally unimaginable,

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just happens to be the frequency range at which molecules and atoms are shaking.

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So if we can excite the molecules and atoms with light frequency, we can make them shake faster.

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And if they shake faster, they get hotter.

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And if they keep heating up, they will get to a point where, as you saw with that paper, it heats up so much and bursts into flames.

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So that is the mechanism by which light waves convert into something else.

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There is no heat in the beam itself. You are using the light energy, the frequency of the light to stimulate the molecules to move faster.

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The faster they move, the hotter they get, the hotter they get,

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there is a point beyond which if you shake them too hard, they will literally just destroy themselves.

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How this laser machine works, is it takes this frequency and it amplifies it through this lens.

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It doesn’t change the frequency. What it does, it changes invisible but bright light into very, very, very bright light.

Transcript for Laser Beam Safety (Cont…)

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Just like when you focus the sun with a magnifying glass onto a piece of paper and it burns or scorches the paper.

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That’s exactly the same principle that we’re using here. OK, so here’s our laser beam and we’re now going to send that laser beam through a lens and

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that lens is going to focus the laser beam like this to something called a focal point.

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Now you’ve seen how dangerous that beam is before we even send it through this lens.

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But look what happens here? We’re compressing it down to an incredibly small point and it becomes very, very, very,

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very dangerous at this point because the intensity of the light is so high at that point, that

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it doesn’t just go up and shake the molecules a little bit. Because the intensity is so high,

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it shakes them incredibly fast and incredibly quickly. It can’t shake them any faster than it’s breakdown point, its destruction point.

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Once it gets to that temperature, it will burst into flames.

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The only thing about concentrating the light is it happens quicker.

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So that’s the whole point of the lens in this setup, is to make the intensity of the light so great that things happen very, very quickly.

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Obviously, light rays only travel in straight lines. It’s relatively not dangerous before it hits the lens.

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And after the focal point, it’s relatively not dangerous.

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Again, down here, relatively.

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I still wouldn’t want to put my hand in the way of either that beam there or this beam here.

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I’m going to give you a demonstration of what I mean about the intensity of the light having different effect.

Transcript for Laser Beam Safety (Cont…)

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The focal point here is about 20 millimeters away from the end of this nozzle.

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Now the beam is starting to fire down into that water and nothing is happening.

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Get the idea, as I move closer to the focal point.

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The energy concentration is so high, it immediately creates steam.

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I purposely used water here, because you think of water as being transparent in the same way that you think

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of glass as being transparent or my glasses as being transparent because you can see light through them.

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This is one of the strange properties of light. Not all laser beams are exactly the same.

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What I’m going to talk about in this session, this specifically applies to this CO2 laser light.

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Now, this has got a very special wavelength. Ten point six microns, that’s ten point six millionths of a meter.

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Now, just to put that into some sort of perspective. Oh, dear, I’ve just pulled two or three hairs out of my head.

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Those hairs are approximately 50 microns.

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So those hairs are five times thicker than the wavelength of this light.

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Those wavelengths are in a part of the electromagnetic spectrum, which your eyes are not sensitive to.

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Your eyes are not vibrating at that frequency. That’s, that’s the reason why they are invisible.

Transcript for Laser Beam Safety (Cont…)

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Remember, back to the jelly and the cake example. Every material has got its own vibration frequency.

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And this frequency here at ten point six microns wavelength is a very broad spectrum vibration.

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This light, it can only see three things.

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Let me just tell you what those three things are. One of them is metal.

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Any type of metal, raw, bare metal reflects, becomes a mirror.

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Look, even this mild steel here, which is mucky and badly scraped on the surface with scratches,

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this will still reflect something like about maybe 70 or 80 percent of the light,

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that’s fired at it. Put a piece of aluminum down and it will probably reflect 99 percent.

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So we use metals on this machine to act as mirrors, to send the light around the machine.

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Group Two, I’m going to use the word salt.

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No, it’s not salt in the condiment style of salt.

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This is a special group of materials, salt like materials, which are crystalline.

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Now, this might look like yellow glass to you, but it’s not.

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It’s a material called zinc selenide, and it is a salt like material.

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It’s harder than salt crystals. But believe me, if you drop this very far, it will shatter.

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So treat your lenses very carefully. And as you can see through it.

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Yeah. So the laser beam can see through it. That’s just one of these salts.

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There is another one in the group, which is called gallium arsenide.

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Can you see anything through it? No, you can’t. This frequency passes right through this unaffected.

Transcript for Laser Beam Safety (Cont…)

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This is transparent to this frequency of light, and that’s one of the weird properties of light. Here we’ve got our

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salt like materials, which is group two. And then we’ve got group three, the third thing in the ten point six micron Wavelength Universe.

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And there it is. So are your eyes made of this material?

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Are your eyes made of that material?

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Your eyes are in this group and that means that this frequency of light will shake your jelly, it will shake your cake.

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It will have an effect on everything else. And remember, as I shake things and make them shake faster, they get hotter.

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If these waves hit your eyeball, what they will do,

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they will vibrate the front face of your eyeball because that’s the first thing that they’re going to come into contact with.

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And you get this lovely smell of frying bacon. You won’t be able to see it, but you could smell it.

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OK, I’m being rather rude and crude there, but that’s a fact.

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If you put your eye and it’s an impossibility virtually to get your eye in the way of a laser beam,

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the laser beam, regard it like a bullet that somebody fired at you.

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If it misses you by half a millimeter, it’s not dangerous.

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It is only dangerous if it hits you. And that’s exactly the same as this laser beam.

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You can stand here and it’s not going to jump out at you.

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It’s not got any sideways ray that are flying out and are going to affect your eyes.

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When the laser beam comes out of the laser tube, it starts off at this diameter.

Transcript for Laser Beam Safety (Cont…)

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And technically and if you want to imagine it this way, that laser beam looks like this.

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It doesn’t spread out, it doesn’t send rays out that are going to bite you. No, it stays just like that, a continuous stick of light.

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It’s a special form of light which remains bound together.

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It doesn’t need an outer casing. In reality, it’s not quite as simple as that.

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But nearly, this beam will gradually grow like this.

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And the amount of growth is very small. For a CO2 laser tube, the growth is something like about three millirads.

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What the hell is a millirad? Well, very simply, what that means is three millimeters

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of beam growth per meter.

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So if that beam length is a meter long and it started off at seven millimeters, it will finish up at 10 millimeters.

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But that’s as much as that beam is going to distort. It’s certainly not going to jump at you and be dangerous.

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So the only danger that you’re going to get, is if you put your eye in front of the beam somehow,

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or you have to be stupid enough to put a piece of metal underneath the laser beam in some way,

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shape or form, accidentally or otherwise, so that the beam reflects off there like a pool ball coming off a cushion and flies out at you.

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So never put metal in front of the beam, especially down here.

Transcript for Laser Beam Safety (Cont…)

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OK, I know we’ve got a table. And trust me, if you fire that laser beam at the table and I put my hand up here,

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it could be dangerous depending on how much power I’m firing down at the table,

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because remember, 70 percent of that power is going to get reflected back up.

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OK, so it’s going to be slightly diffused and you may well find it hot on your hand.

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And I mean hot. All right, you’ll be able to feel it because it is infrared radiation and, you know what

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infrared radiation is. It’s that stuff that comes from the sun, from radiators, from fires.

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It’s things that you can feel it’s hot. It’s not hot at all.

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All it is is energy, which is heating up the molecules in your skin.

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There is no heat in that light, I keep reinforcing that, the light is busy affecting the molecules that it impacts and that’s why you feel heat.

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So I think that’s probably about as much science as we need to talk about.

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Now, let’s talk about those guys that want to sell you expensive safety glasses.

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What do they know?

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Well, they know that you’re frightened of a laser beam. As you rightly should be, because I’ve already shown you what it could do to your eyes.

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Yeah, it won’t set fire to your eyes, but it will certainly turn them into lovely fried bacon.

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I purposely raise this up so that you could see steam being produced.

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OK, now you therefore know that energy is passing through that mirror.

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There, going down through the lens and heating up the water. What happens if I put my eye in front of that?

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Yes, but look what’s happened. Now

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I’m going to completely destroy these glasses. I want you to watch the steam.

Transcript for Laser Beam Safety (Cont…)

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Steam, no steam, no steam. Now,

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I think you probably can imagine that if you happen to put your eye in front of the laser beam and you saw flames in front of your eyes,

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you would jump out the way pretty damn quickly. OK, now, if we take a look at this side of the glasses, they’re completely undamaged.

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This side, yeah, we’ve done a lot of damage to that material, because that is not metal,

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that is not one of these special salts, that is a polycarbonate material which they use to make these lenses with.

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And that has absorbed all the light energy that’s been fired at it. It’s vibrated the molecules on the surface of this material and made it disappear.

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It’s burnt it.

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Now, exactly the same thing will happen to glass because, look, this is transparent and therefore you would think that light would pass through it.

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There’s a demonstration that the light does not pass through it.

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OK, it’s absolutely undamaged on this side.

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This is unlike the visible light where certain types of laser will pass right

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through this material and right through to the back of your eyeball and the retina,

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and it will damage the back of your eyeball and make you blind.

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This is a different sort of light. I’m not saying it’s any safer, but that’s why I’m saying you need to understand the differences between the

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way in which light, different frequencies of light affect different materials.

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This is not just I’ll wear a pair of glasses and you’re safe.

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So I always have to wear some sort of reading glasses. So I’ve always got these cheap glasses on.

Transcript for Laser Beam Safety (Cont…)

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You don’t need anything expensive, right, to protect your eyes, just industrial safety glasses.

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These are polycarbonate. I’m not going to destroy these because I use these for people that come in and visit me.

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And are a little bit frightened of the laser machine, especially when I’ve got the lid open.

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I haven’t got time to tell them that it’s not particularly dangerous. For something like about two dollars,

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you can go on to eBay, and you can get some rather nice looking Rayburn style ski glasses almost, safety glasses.

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So you don’t have to look like an idiot. Spend two dollars. Don’t spend the twenty or the two hundred dollars on these special safety glasses.

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There is no danger other than those I’ve explained to you here.

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That’s why I can operate this with my camera. And the lens is not at risk.

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I can operate this with the lid open and my eyes are not risk either with or without glasses.

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But I always wear glasses anyway, so I know that my eyes are protected.

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But you protect your eyes, but it doesn’t stop you burning your skin around the outside of your eyes if you happen to get a flash.

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Remember, everything is a group three material, including your skin and your clothes.

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So nothing is safe, but everything effectively is safe if you don’t put anything in the way of the laser beam.

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Remember the bullet passing by you, missing you by a millimeter. That’s the level of danger

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That you’re in. OK now, when you come to cut organic materials.

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This is a piece of MDF and here we’ve got a piece of plywood or wood, leather card, something like that.

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When you’re in engraving or cutting, what I want you to do is to watch this surface here and you will see a bright white light.

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Now, that bright white light is very, very intense.

Transcript for Laser Beam Safety (Cont…)

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That’s effectively a carbon arc. It’s just like looking at an arc welder or looking at the sun.

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It’s not incredibly intense because it’s so small.

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But what it is doing, it’s sending out UVB radiation. Within that very bright white light,

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there are nasty spikes of dangerous light. Now, you know what UVB is?

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It’s the stuff that gives you sunburn. It’s the stuff that can affect the cells in your body. That is a far more insidious

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form of damage that you can do to your eyes than the laser beam itself.

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It looks harmless, but that is what you need to be really careful about.

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You could look at it for a few seconds. If you close your eyes and you see white spots before your eyes, then you know,

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you’ve overstressed the cells in the retina at the back of your eye, just like looking at the sun. For a few moments,

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it’s not a problem, but don’t spend time looking at the laser beam as it works.

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It’s a fascinating thing to do and it’s almost hypnotic. Ten, fifteen seconds at a time,

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not a problem. Look away. Give yourself, give your eyes a few moments to relax.

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Go back and look again. OK, now I’ve closed the lid of my machine. Now this machine is very well made and it has glass, real glass for windows.

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You will find the screen, or windows on your laser machine could be made of two other types of materials.

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So this is glass. You can look at UVB light through this glass because UVB light does not pass through glass.

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You can sit behind a sheet of glass with bright sunlight outside.

Transcript for Laser Beam Safety (Cont…)

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You will turn into a lobster, but you will not get sunburnt, you will feel the heat, but the UVB light is filtered by glass.

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This is the strange properties of different light frequencies.

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UVB is a shorter wavelength light and it does not pass through glass.

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However, it does pass through acrylic.

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So if you’ve got an acrylic cover on your machine and that’s what most covers will be,

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the UVB light will pass through and your eyes are still at risk.

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Even when you close the lid, put a pair of sunglasses on and it’s just like looking at the sun with sunglasses.

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It will filter those UVB rays out. Don’t get overstressed about it because it’s not highly dangerous.

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It’s just something you shouldn’t spend time looking at. If you’ve got glass, the rays get filtered out.

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But the one thing that isn’t filtered out is the intensity of the light.

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OK, so there are two dangers with that bright light. One is its intensity.

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And because it’s a fairly small white light, but it’s a very intense beam of light, it will have a long term effect on your eyes.

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If you spend a lot of time studying it, staring at it and looking at it 20, 30 seconds at a time, is not going to damage your eyes.

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The UVB is not going to damage your eyes, only if you keep doing that over the long term.

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So the other thing is polycarbonate like my glasses here, they do also filter out the UVB rays.

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So when I wear my glasses, I’m immediately protected against the direct effects of being hit by that bullet.

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And I’m also being protected against the UVB light rays that are generated when I cut or engrave organic materials.

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Yes, this is a dangerous piece of equipment and you’ve seen how dangerous it can be.

Transcript for Laser Beam Safety (Cont…)

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OK, so now you’ve got all the science facts which allows you to, first of all, understand how your machine works.

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How it may or may not fry your eyeballs and C. why you should or shouldn’t spend a huge amount of money on safety glasses.

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Please do not fear this technology. It’s fantastic. Just understand it.

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Thanks for your time and your patience. And all I can say to you is enjoy the hobby and cut and engrave safely. Catch up with you in another session.

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Bye for now.

Transcript for Laser Beam Safety

Disclaimer

Last updated August 26, 2021

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