Thanks @Anette_Henningson, it would be great to visit and see the setup there. My brother actually lives in Canada so maybe I’ll swing by next time I visit him.
About the study that Björn is drawing on, he actually sent me a pic of it yesterday.
I’m inquiring with the organising that publishes it - CADS - to find out if there is an English version available.
you keep trying to say there’s a difference between cutting and etching. there’s really none.
if anything it’s going to be worse to be etching since most of the surface that has extra treatment on top of it that’s getting burned off.
you be also failed to see my point that, it’s less of a health concern and more of a concern that the shear number of users makes it more detrimental for the Makerspace to allow cutting materials that are even slightly more dangerous for the machines.
we are trying to maximize the uptime of the machines, if that means you can’t cut certain materials at the space, it’s a sacrifice the committee has decided to make.
Pearce… am not arguing just trying to understand for my own knowledge. I firmly agree if something can hurt the lasers don’t cut it.
I have loved learning how to design and cut leather items on our lasers. I’d love to see chrome tanned leather be approved for use, but only if it is safe. That’s why I enjoyed hearing the science behind it, and further researching leather.
Is the caution lasering the chromium salts and it potentially putting off chlorine gas and that can damage the laser or not knowing all the chemicals in chrome tanned leather?
yes it’s prudent for us to cut “known” materials. basically if you can’t pin down what’s in the thing you are wanting to cut you shouldn’t.
if you REALLY need/want to cut something unknown, get your own laser or buddy up with someone who has one that’s not a community tool.
Personally, I’d love to get my own laser, but would need to get one with a bed size large enough to justify it. This year I’m focusing on 3D printers, so maybe 2023 is the year for laser.
I really don’t want to hinder more than help, but based on your response I’d feel negligent if I didn’t ask… should we even allow veg tan leather then?
This quote from above surprised me.
If the hesitation to use chrome tanned leather is not knowing what all is in it… then perhaps we don’t know what all is in veg tan either.
dunno, it’s not my committee, so not my choice.
I’m just trying to explain some of the hubbub about how it turned into “omg mustard gas” - I’m not an expert in the area.
I’m comfortable using veg and chrometan on my personal laser, but I watch and clean it carefully.
think of it like the “no yellow pine” or “no salvage pallet wood” rule in woodshop. it’s to protect the tools from being overwhelmed by the buildup of small issues from many users caused.
Very similar processes yes, but similar to using baking soda and baking powder when making a cake, this small change will yield vastly different results.
I’m not sure what you mean by better… Here’s an old piece I had on hand that was etched:
Are you going for a darkened/black look?
If you use my process that I explained earlier (emphasis on the water), that will help prevent any pulling/shrinking or charring of the leather caused by the heat. If you are going for a darkened or black look, my suggestion would be to infill with paint.
It’s very pungent smelling. I’ve had my fair share of the gas in my career.
It is also what halide leak detector torches create to find refrigerant leaks. The flame turns from blue to green.
Wow! I didn’t realise that was possible. The laser machine that we bought mentioned soaking the leather in water and we tried it but couldn’t figure out how it was meant to assist with cutting or engraving. I now have my answer. This is useful if anyone wants us to specifically avoid burning the leather.
Yes, we’re going for the darkened/black look.
There is a little soot residue when it comes out of the laser but just an ordinary eraser removes this. We then brighten it up with a rub with some leather balsam. The leather I used here is the wheat veglook from Leather Link which is fully chrome-tanned.
I use the lasers to cut vegtan on occasion. My approach is to thoroughly “case” the leather by getting it quite wet, allowing the water to penetrate deeply, and then allow the leather to just begin to dry on the surface. After cutting/etching via laser I wash it again, which removes the bulk of any char created and also nearly eliminates any lingering burned-hair aroma.
Examples
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This book cover has an etched front which was then tooled somewhat. The spine and the stitch holes were also cut by laser.
These knife sheaths were cut and the stitch holes drilled on the laser. The basket weave was hand-tooled and the sheathes wet-formed over wooden bucks. FWIW, this file is available in the Leatherworking folder on the Committee drive if you want to make one for yourself
These notebook covers were cut and etched on the lasers. Stitch holes were also drilled. Again, these all used the case, cut, and rinse approach.
The sheaths and notebooks were donated to a horse trail non-profit to pass out as thank-you award gifts to volunteers.
OK, let’s go with your analogy of baking soda and baking powder. Baking soda is simply sodium bicarbonate which is also the main ingredient in baking powder except baking powder has acid added to it. This is the ‘small change’ that makes all the difference. When baking powder is mixed into cake ingredients and put into the oven, there is a chemical reaction which releases carbon dioxide and causes chemical leavening. The reaction is:
NaHCO3 + H+ —> Na+ + CO2 + H2O
If we make the analogy with leather, then both veg- and chrome-tanned leather are made from animal hides but the issue is that extra ingredient - the ‘small change’ - that will yield ‘vastly different’ results when lasered. I’m trying to establish what this extra ingredient is and the mechanism by which it yields such vastly different results. I’d like an argument that uses scientific evidence to back up the claim.
The biggest difference between these two types of leather is the substance used for the actual tanning process - veg extract on the one hand and mineral salts on the other. The main concern that people have with chrome-tanned leather is that, in the past, it contained significant levels of hexavalent chromium which is known to be carcinogenic. That is presumably why the DMS table for materials that can’t be cut or etched included chrome-tanned leather: ‘Freaky chemicals including chromium, are used for the tanning process and will be released/burnt when lasered.’
But if we understand that hexavalent chromium salts are no longer used in the tanning process but rather harmless trivalent chromium salts, this can’t be the extra ingredient that makes the big difference. I also made it clear in the thread above that the conversion from trivalent chromium to hexavalent chromium is a redox reaction that takes place under specific conditions which are not present when simply lasering a sample of leather (a combustion reaction).
@jast said that he expected someone to edit out the phrase ‘freaky chemicals like chromium’ in the table and @Brian admitted that the inclusion of the word ‘chromium’ was a mistake but said that the characterization was ‘spot on’ for your makerspace. In other words, there are other ‘freaky chemicals’ used in the tanning process that are released when lasered.
What are these other chemicals? @Brian suggested chlorides and @jswilson64 added that the problem is not so much health and safety but damage to the laser machines. @PearceDunlap agreed with this and argued that even if a little chloride is released on each cut, it will hurt the laser machines in your makerspace because of the 1000s of cuts that are being made. Now chlorides are added to leather in the pre-tanning process, specifically in the ‘curing’ and ‘pickling’ phases where NaCl are used. But the problem with this argument is that both chrome-tanned and veg-tanned leather are treated with these chlorides so they can’t be that ‘small change’ that yields’ vastly different results’. If you are banning chrome-tanned leather because of the chlorides, you should also ban veg-tanned leather because they both contain the same chlorides that - according to someone - will be released when lasered.
The reason why I mentioned ‘similar’ is because of what Bjorn said to me:
Note that he says ‘exactly the same’ except for the veg extract and chrome salts - which we’ve already ruled out - and Magnesium oxide which is used only in the chrome-tanning process. By your baking soda and baking powder analogy, are you suggesting that MgO is that ‘small change’ which makes all the difference? We could look into it but as far as I know, MgO is used to neutralise the acid in the pre-tanning process so the trivalent chromium salts can penetrate the leather. It is not poisonous or carcinogenic and it certainly doesn’t contain chlorides. It therefore doesn’t fit the argument brought forward by @Brian and others.
I’ll toss in my two cents.
While I appreciate a good chemistry discussion as much as the next person, DMS committees are well within their right to regulate/prohibit the use of materials, or practices that they feel ‘may’ (notice I did not say not shall) present a ‘potential’ risk, to either makers or equipment.
At this time, there are no reliable manufacturing controls to ensure a consistent product, possessing a reliable MSDS for all types of leather labeled as ‘chrome tan leather’. And as this type of leather is being manufactured from all corners of the world, I doubt there ever will be.
That’s why the Laser committee upheld the existing ban from previous Laser committees when we were chairing / vice-chairing laser back in 2018. Current/future committees can and should revisit this topic periodically, if only to ensure that nothing has changed with regard to these safety and risk variables.
In my experience, the vegetable tanned leather that enters our makerspace is just that. Simple vegetable tanned leather. If the chromium tanned leather is the same, simple chromium tanned leather, then you have a solid argument.
In my experience, the chromium tanned leather that enters our makerspace is never just chromium tanned leather. It’s dyed. It’s treated. It was fished out of a dumpster. Or donated. The provenance cannot be determined. The chemical makeup can only be determined by careful analysis. I’ve stated that already. You’ve repeatedly ignored that.
The problem with your argument is you’re adding nothing new.
You’re pushing back against organizational rules at a volunteer-run educational nonprofit, halfway around the world, for what reason exactly?
You’re an academic laser user, do you have any controlled study data, maybe using one laser just for veg tanned leather and one for whatever materials the user wants to cut, to see the long term effects on the mirrors and lenses?
What guarantee do you offer DMS that allowing chrome-tanned leather in the lasers is ok “because Dr. Kloot says so”? If we suffer downtime or damage, how do we hold you responsible?
OK, I think I’ve made enough of a nuisance of myself on this forum and this is taking up far too much time so I’m outta here. As my swan song, let me tell you a story.
A while ago I was at Woodhead’s which is probably the oldest leather merchant in South Africa. Here’s a pic…
…and I overheard a lady who said she was buying leather for her son’s project say, “I must be vegtan, it can’t be chrome-tan leather”. And the way she was insisting got my attention because she was saying it with a kind of urgency. I thought it’s strange that I am using chrome-tanned leather in our laser with no problem but people seem to have something against it. So I Googled and found quite a few sources that indicate that chrome-tanned leather is really bad stuff, that it even emits toxic chemicals that can kill you when you put it in a laser. Needless to say, the DMS table came up among them.
I thought it’s quite ridiculous to imagine that a company could sell you a laser machine and even advertise that it cuts leather but fail to mention that 90% of the leather out there - the chrome-tanned variety - is lethal. And I’m working with the stuff myself on a daily basis! So that’s what got me interested. I think it’s utterly fascinating that people might have an idea about something which they gleaned from the internet but which is not reliable. And this grows in the manner that @PearceDunlap described in his post above until it’s commonly accepted as fact.
So did some digging around, and made a video for MaxLaser, the company that sold me the laser machine. Then I thought what better way to test the ideas in that video than post it to the people or forums that I ‘called out’ in the video. So I sent it to Ryan James of Little King Goods with no response (as yet). And I posted it here in DMS Talk. There was some petty opposition initially - @Brian didn’t like the soundtrack on my video and @jswilson64 implied that I was trying to drive views to my YouTube channel 
- but on the whole the engagement was amazing. Thank you all for giving your input and for helping me get my head around some of the arguments and concerns.
That’s part of the answer to your question @jswilson64, about my reasons for posting here. The wonderful thing about science is that I don’t have to do an empirical study for every question that you want to address and it doesn’t matter where you are in the world. There are universal laws that apply and, through logical reasoning, you can make deductions and have a good chemistry discussion and trade ideas. I never expected you to just believe me because I, Dr Kloot, said so 
. For example, the argument that I made - thanks to Bjorn - about the pre-tanning process of veg- and chrome - being almost identical - you don’t have to take my word for it but investigate for yourself, from reliable sources (visiting a tannery is something that I’d love to do) and then draw your conclusions.
I wasn’t pushing back at your organizational rules but your organizational rules contain ideas that people all over the world are reading and taking as fact. What I’m interested in is the scientific basis for these ideas. From my side, it looks like everyone would just be happier if they could say, 'Because our rules say so!" and not worry about the detail.
I appreciate @Scott_Blevins’s point about the due process of the Laser Committee and the perfectly justifiable reasons for why it might uphold the ban. I totally agree with the point about the lack of control over the leather industry, thinking specifically of hexavalent chromium levels in leather from developing countries, but of course I understand that it remains a potential risk for your community and it’s better to err on the side of caution when it comes to your members and your machines.
On this point - and I’m sorry that this is so long - I actually spoke to the buyer at Woodhead’s and she told me that she was asked by some tourists from the EU about Cr6+ levels and she didn’t know what to answer them. So she inquired with one of the tanneries in South Africa they buy from and was invited her on a tour to show her the process. She told me that the tanneries are run like hospitals the way they are so clean and she was confident about the Cr6+ levels after this.
Funny thing is, I visited Woodhead’s today to ask where they get their vegtan from and, to my surprise, the lady on the floor told me that they buy it from all over, both in South Africa and abroad. Countries she mentioned were Brazil, India and Germany! She said it’s the same with chrome-tanned leather. This brings up two things for me:
- How does the buyer that I spoke to know that the chrome-tanned leather they are getting in it not off the charts for hexavalent chromium? She only visited a South African tannery. I’m sure they don’t test every batch so it is a bit concerning and I want to talk to her further about it. I’m not directly affected because we source our leather from a tannery that I know is reputable but the potential risks are there, I admit.
- How can we be sure that the vegtan leather is what we might call ‘real veg’, i.e. is not first chrome-tanned? @Brian, on this let me share something new with you: Bjorn told me that only 1.5% of vegtan leather produced in South Africa is completely plant based from start to finish but for the rest, it is acceptable practice for tanneries in South Africa so take the ‘wet blue’ which is first chrome tanned and then retan it with 30-40% veg extract and sell it as vegtan. Incidentally, regular chrome-tanned leather is re-tanned with 5-10% veg extract to give it some character and colour. I wouldn’t be surprised if tanneries elsewhere in the world are doing the same. Perhaps it’s different for your makerspace and the industry in the US but I wouldn’t be surprised, with globalisation being what it is, that you are getting all sorts of vegtan from your merchants and this is getting into your makerspace. You would know better than me but it isn’t easy to even tell the difference between veg and chrome just by looking at it and feeling it so the possibility is there.
I have a few more things to say about the inevitable range of quality that we get with chrome-tanned leather - because of the efficiency of the process - and this being a reason to ban chrome-tanned leather. I do get this @Brian but if it is the reason, maybe it should be stated as such. And on the point dyed and treated chrome-tan being a problem, I found this on the website of one of your local stores which indicates that vegtan is also subject to dyeing and treating and so may not be just ‘simple vegetable tanned leather’: Dyed | Springfield Leather Co.
Anyway, something to think about and I hope there are no hard feelings.
Lastly, thank you to @Taylor_Quimby and @HankCowdog for sharing about wetting and washing vegtan. I now have a ninth ‘no char’ option to include in my next video.
Best, Bruce 
@Team_Moderators May I suggest this thread be closed? Looks like the OP has said everything they felt like they need to say.
Took ten seconds to search and found this. Sounds like there’s some nasty stuff in chrome tanned leather that you don’t want to breathe in.
Are some less toxic than others? Maybe. Want to risk it? Going to test the toxicity on every batch? Sounds like the policy at DMS is reasonable.
The thread seems civil so closing it seems unnecessary at this time. Another moderator can close it if they think it’s necessary.
I’m with @PearceDunlap, DMS made the decision based upon best practice for a community used machine and we should honor it. If you want to cut chrome tanned leathter buy yourself a laser and make your own decision about toxicity.
It was an interesting discussion, but I prefer to error on the side of safety. Same with welding galvenized metal. It is done all the time in the commerical world, but in a well ventilated or completely gas masked environment. That’s how we did it in the air force. 5 Vital Things to know on Welding Galvanized Steel Safely This doesn’t mean DMS should allow it.