Right, but I think the question a couple people are posing is /does/ this material damage the machine?
Obviously we have rules against various things that damage people and machines, I certainly don’t dispute that.
@apparently_weird, I have made some progress on finding out the chemicals used in chrome tanning. I had a look at the information you provided via that CSIR link but I found it difficult to make sense of. So I contacted our most regular supplier Leather Link (http://www.leatherlink.co.za/) to try to get some insight. They gave me the details of an agent for the German chemical company, Lanxess, that supplies the chrome tanning chemicals to all the tanneries in South Africa. The name of the agent is Björn Johanssen (originally from Sweden) and he was very helpful. He confirmed a number of things that I mentioned in my video, including the details about the salts of hexavalent chromium no longer being used but trivalent chromium salts instead. In fact, he said that when he was an apprentice 30+ years ago, they used to handle chromium (VI) salts with their bare hands but when the dangers of exposure came to light, this all changed. We had a long conversation and I explained the issue we are grappling with to Björn and he provided some really interesting information.
What I was surprised to learn was how similar the veg tanning and chrome tanning processes actually are. Via a WhatsApp message later on he wrote: ‘Something I thought about now is that the only difference in the tanning process between real veg and chrome tanned leather is the veg extract and the chrome tanning salts. All other chemicals in the process is exactly the same with the exception that tanning with veg needs no Magnesium oxide. Everything else is the same. So why there should be toxic fumes when burning chrome tanned leather baffles me.”
I followed up with some searching on the internet and found this video - Chrome Tanned vs. Vegetable Tanned Leather, Explained - YouTube - which compares chrome- with veg-tanned leather. At around 4:30 mins and again at 6:50, the narrator confirms that the steps in both processes are the same before tanning. He just mentions the dehairing process and the rinsing process where the pH is lowered with talcum. A quick search on the internet shows some more sub-processes (there is obviously some variation across the range of tanning processes) but they include:
- Curing with NaCl
- Liming with an aqueous solution of Ca(OH)2 as well as sodium sulphide (Na2S) and possibly other salts
- Bating with proteolytic enzymes to break down the fat remaining in the leather. Examples of such enzymes include Ficin which occurs in the latex of tropical trees of the genus Ficus subgenus Pharmacosyce, Moraceae (Oje trees).
- Pickling with NaCl and sulphuric acid (H2SO4)
What happens after the tanning process is relevant because this is where the leather is dyed, rolled and/or waxed etc. What I found out is that many tanneries produce both veg- and chrome-tanned leather so there is no reason to believe that the one set of chemicals used is better for health and safety (or laser machines) than the other. In South Africa, most tanneries are in fact finishing plants, i.e. they buy the ‘wet blue’ from the guys who tan from the raw hide and re-tan, dye and finish it for their market niche.
So we are getting closer to understanding the issue that @trapezium mentioned about the ‘unknown cocktail of potentially toxic substances’. You can do your own research but other sources bear out that the veg tanning process uses many of the same chemicals as chrome tanning so the idea that chrome-tanned leather produces toxic fumes when lasered - as long as we accept that hexavalent chromium is not the issue - does not make sense.
I have more to say about a simple test to tell the difference between the two - something else that you mentioned in your post - but I’ll leave it here for now. If you need the details of Björn I can provide them. He was willing to have a video call with me to talk about these issues so I’m sure that would be a possibility with you or whoever else is interested. Alternatively, you can contact a tannery or a Lanxess (or equivalent) agent on your side.
5 Likes
I’ve had my own personal experience with cutting both chrome tan and vegetable tanned leather. Even if you want to be completely ignorant to whatever chemicals that chrome tan could release, you can’t be to the level of quality cut that it produces.
Although I do feel like we could be missing out on a very enlightening conversation regarding its use in the lasers, I also think one could be saving some time if you just used vegetable tan just for the sake of quality.
Any leather project you embark on using the lasers will come out better, 𝗵𝗮𝗻𝗱𝘀 𝗱𝗼𝘄𝗻. This isn’t like wood where limiting one kind would limit your creative reach. You are not missing out on anything new or exotic by using it.
And if anybody wants/needs help cutting leather, send me a message. I have a few trade secrets to deal with charred edges. 
5 Likes
Hi @Taylor_Quimby,
Good to hear from someone who lasered chrome-tanned leather and lived to tell the tale. Some people believe that it emits toxic - even lethal - chemicals when lasered. 
What is true from your experience is not true for mine. But this obviously depends on the range of leather that we are able to source. Perhaps you don’t have access to the range of chrome-tanned leather that I do but, on the other hand, perhaps I don’t have access to the veg-tanned leather that you do.
The reason I made the video that I posted in this forum was to serve as an introduction for the video that I am busy with now. I felt that I couldn’t talk about the variations in types of leather and how they take to lasering, without first addressing the main categories of synthetic, chrome- and veg-tanned, and some of the misinformation around chrome-tanned leather. This done, I’m getting into a video where I cut and engrave samples of various types and compare the outcome. One of the types is actually a combination of chrome and veg-tanned leather, called the ‘veg retan’. There is also a type that looks and feels like veg-tanned leather but is actually fully chrome-tanned. Leather Link is the company that produces this range and they call it ‘veglook’.
The samples in the photo below still need to be cleaned up since they are straight out of the laser but you can already see that some are looking better than others. Any guesses about which is which?
And I am interested in your trade secrets about dealing with charred edges. Please share
Charred edges help please! Please include charred edges of stitching holes. 
I’m in the camp of figuring out some way to allow Chrome-Tan to be lasered. I have some really nice SB Foot that I want to make duffles/backpacks out of but have refrained to stay compliant. I do see one of my favorite creators (Creative Awl) lasering chrome tan and his stuff comes out stunning.
What’s the skinny on oil tan?
IIRC, most “oil tanned” leather is chrome tanned first. Or somesuch.
That’s what someone told me at the space, but Tandy leather insisted it was not chrome tanned. I did come across something that mentioned that oil tanned has fish oils that replace the veg tannins.
I do wish I could do more with my oil tanned hide though. Before I was told it was chrome tanned I made some great bags before I stopped to be compliant.
1 Like
I find the Leather dictionary a really good source of info. Interesting what they say in this snip about oil tanning being a form of “false” tanning.
https://www.leather-dictionary.com/index.php/Tanning_leather
I suppose oil tanning could also refer to the application of oil in the finishing process after its been tanned with chrome or veg.
It may depend on the tannery. I bought some of this from Springfield Leather:
I asked via email and they confirmed it’s chrome tanned.
From what I understand, before the effectiveness of chrome salts were discovered, various substances were used in an effort to preserve the leather. Apart from vegetable tanning, there was the use of fats and oils (including animal brain!) but this didn’t really do a good job, hence the notion of “false” tanning. Tanneries today obviously need the leather to be properly tanned in the cheapest way so they use chrome but then they finish it off with oils and so ‘oil tan’ is just the name given to the product, as with Springfield.
I was told in Boy Scouts about leather tanning that, “every animal has enough brains to tan their own hide.” The double meaning fully implied.
2 Likes
I’ll give a couple different techniques.
If you’re just looking to cut out shapes from the leather the best way to avoid charred edges all together would be choice to laser a template of some expendable material such as tempered hardboard, MDF, or thin acrylic. The important part being that it’s a hard material. Because paper templates are a pain in the butt to work with in comparison to a rigid one (and let me just save you the time - posterboard is not stiff enough). But of course you still have to do the hard work of cutting around the template so that was just a gimme… 
The technique I use is going to be best used on vegetable tan because of its ability to readily absorb water. While it can be used on other types of tans I can tell you that the results aren’t going to be as good.
Completely soak your pieces of leather in water before placing them in to cut. Not to the point of dripping but to the point where they will not absorb any more water. Have a spray bottle on hand for longer cuts as the letter will dry due to air assist and the heat generated by the laser. Periodically pause your cut to spray the leather so that way it remains wet through the entire process.
For speed and power… You’ll need to find a balance of how much time you want to spend at the laser and how much you don’t want those charred edges. But it is most important for avoiding charred edges is to use the lowest amount of power no matter the speed. You will find that the best cuts are ones done in multiple passes.
Now here’s where it gets different. Instead of cutting out your design and stitching holes with the “Line” setting, you will be using the “Fill” feature. So instead of the laser cutting out little tiny circles for the stitching, the laser will be running over it like a rastered image. Making multiple passes over these stitching holes will slowly disintegrate the leather with minimal charring. Remember to keep the leather wet in between those passes so that it’s consistent through the whole process.
However, cutting stitching holes this way is not as straightforward as it may seem. While the laser will make quick work of stitching holes better in a horizontal line, vertical lines would take much longer if not accounted for. To speed the process along for vertically lined stitching holes, assign them to a separate layer. For that layer, change the laser’s scan angle to 90°. This will prevent the laser from spending an excessive amount of time trying to do horizontal passes on individual holes for a vertical line.
If you have the patience and the extra time, this principle can be applied to the perimeter of your designs as well by adding an offset so that the laser can “Fill” a thin line perimeter instead of cutting it. You can also take it a step further by sectioning object perimeters so that the laser is moving efficiently instead of trying to cut vertical lines horizontally. But believe you me that is a very tedious process in comparison… 
I hope that made sense, let me know if it didn’t and don’t hesitate to ask questions. The only stupid questions are the ones never asked. 
I know it’s kind of hard to see the edges and stitching holes, but here is a name tag that I did for my dog’s coller using my method.
1 Like
ah there it is. you are fighting from the wrong end of the extreme.
I hear a lot of training saying things like “you can’t cut chlorides, it turns into mustard gas” which isn’t true at all but it stops people from cutting them and I cant be bothered to stop a class to correct it.
it won’t kill anyone this is true. but it can hurt the machines, and the issue isn’t the one person doing a few pieces… it’s the over 1000 members who can. its death by 1000 cuts for the machine.
not including the heavy hitters who are running an Etsy or bigger business on our machines.
tldr you can cut all the chrometan and vinyl records you want on your personal machine at home.
4 Likes
Hey @PearceDunlap, I was referring to this comment. According to @JoshW, the more important issue is the lethal cyanide gas that can be created when lasering chrome-tanned leather. I mentioned in a thread above that I want to see the reference for this because I suspect it’s hearsay of someone confusing chrome-tanned leather with synthetic leather which contains PU which does release cyanide gas when burned.
I still haven’t seen the reference for chrome-tanned leather containing chlorides that would be released when lasered. It sounds like a good argument because we know that PVC (and also leatherette) does release HCl (correct, not mustard gas) and over time this degrades laser machines. I have seen photographs - and I’m sure you have too - of laser machines that were used regularly for PVC and the corrosion is visible. It’s clear that the HCl is combining with water vapour and turning into hydrochloric acid and this is eating the inside of the machine. With 1000 members using a laser machine, the constant release of HCl will certainly do damage to the machine.
However, the problem with this argument is the following: at what stage of the tanning process do these chlorides find their way into the chrome-tanned leather? Is it in the curing stage (which uses NaCl)? Or perhaps in the liming stage where the hides are immersed in an aqueous solution of Ca(OH)2 but maybe there are some chlorides around as well? Or maybe in the pickling stage where the hides is treated with a combination of NaCl and sulphuric acid (H2SO4)? If in any of these stages, the same chlorides must be present in veg-tanned leather as well because the steps up until the tanning phase are almost identical. And if this is true, then veg-tanned leather should also be banned because of the potential to hurt the machines over time because veg tanned leather will also release these chlorides.
From what I can gather, the possible differences between the two processes are that veg-tanned leather is not treated with sulphuric acid in the pickling stage but we are sure that H2SO4 doesn’t contain chlorides. And I mentioned above that Bjorn said that veg tanning needs no Magnesium oxide. Once again, we are sure that MgO doesn’t contain chlorides either. So it can’t be these differences that are responsible for any chlorides.
The chlorides also can’t be introduced in the actual tanning step because for chrome-tanned leather it’s trivalent chromium salts (which doesn’t contain chlorides) and for veg tanning it’s veg extract. I also don’t see any reason why chrome-tanned leather would need to specifically be dyed and/or finished etc. with chlorides whereas veg-tanned leather would escape such treatment.
Odds are - but I’m ready to hear any scientific argument to the contrary - that people are confusing chrome-tanned leather with leatherette without actually checking the science behind the claims. I have some ideas about why this is happening which I won’t go into now because in repeating things I’ve already mentioned above has made this post far too long.
I’m confused on what you’re asking. Can you state your goal and/or purpose in just a few words?
1 Like
Hmm, the DMS guidelines are not a scientific white paper, I’m sure there are many finer points that can be studied further. The list is to keep members/equipment safe. Here there is a wide assortment of leathers available that may not have the specifics clearly marked for sale, so they could be easily confused. I hope you are able to come by and visit when you can. If you want to share the study by Björn we might have several members that would be interested.
3 Likes
this.
@Bruce_Kloot I skimmed. but I can tell you that the misinformation grew from the game of telephone that is our learning process.
it started as “hey don’t do this because it could make potentially harmful off gasses that have a similar effect to chlorine gas on the metals and the machines” and through the many iterations of classes and people trying to shorten them to keep people’s attention, turned into “OMG MUSTARD GAS”
2 Likes
The gist of your post was that this discussion is very interesting but really a waste of time because vegtan leather is much better in terms of quality. I think you are more focused on cutting and there I admit that vegtan cuts more easily than chrome-tanned leather. However, we are more focused on engraving and for us, chrome-tanned is better. For my next video I’m preparing samples that I have cut and engraved from 8 different types of leather.
I understand that you won’t be able to see the edges for an assessment of the cutting but have a look at the quality of engraving and see if you are able to identify which is chrome and which is veg. The point is, if chrome-tanned leather engraves better, this conversation is worth having.
@PearceDunlap, you have a point there 
And I think what is feeding into this is people’s fear that the stuff might effect their health somewhere down the line - “Argh, hexavalent chromium!” - that they rather just avoid it or any discussion about it because it sounds like freaky stuff.
But I think that something else that is playing into this is economics. Chrome tanning (which can take a day) is way more efficient than veg tanning (which can take months). It’s therefore more cost effective, hence it being responsible for 90% of leather goods. But there are advantages of veg tan leather in terms of the characteristics of the end product and it is more friendly on the environment, this is true. But we need to take a balanced perspective on this, as I believe the video I posted previously does - Chrome Tanned vs. Vegetable Tanned Leather, Explained - YouTube (from 12 mins).
While there are leathers sold as ‘veg tan’ that are actually first chrome tanned, the tanneries who do veg tanning from start to finish want to exploit their market niche and sell themselves as providing a superior product. They are up against stiff competition and their leather costs more, so they amplify the fact that chrome-tanning is less environmentally friendly etc. This company is a prime example - Chrome Tanned Leather - Environmental Impact & Human Consequences - YouTube. While I don’t doubt that there are shotgun tanneries in Colombia that damage the environment, put the health of their leather workers at risk and produce products that are potentially harmful to the end user, the impression this gives is that all chrome-tanned leather is toxic and must be avoided, which is simply not true. That it the intention of this company because the more people they put off chrome-tanned leather, the greater the market for their products.