I have mostly been working with some of my dad’s stock of turquoise, and now have been contemplating doing the thinner pieces. Most of them are pretty irregular on the back (not cut flat, just natural), and the backing material would have to fill any gaps and crevises. I know that many people often use some kind of (black, usually) backing material for their thin slabs. What is that material… where can I get it… is there a commercial name?? ( I think I have seen a few references to Liquid Steel, but really?? Is that what it is?) Any info gratefully welcomed!
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I think you are asking about Devcon.
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Thank you, Christibo! This suggestion has also come up in my other (lapidary) forum, so I guess that’s the answer I needed. I have bookmarked that page. (I guess I will have to think about a Rio Grande purchase: they have several other things on my wishlist!) Big hugs! 
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The Devcon plastic steel is really good stuff, but quite expensive. Unless you are doing a large amount of cabs, I would recommend Apoxie Sculpt. It is an easily workable putty that comes in about a dozen colors that can be mixed to create many more. I use this when I am backing just a few cabs at a time. It is much less messy and is considerably cheaper. It works just as well as the Devcon.
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Thank you for the alternative item, markyboy! I will bookmark that also… certainly a better price (and more size choices), than the Devcon.
Your welcome. I have tried a number of different epoxies and found Devcon and Apoxie Sculpt to be the best and easiest by far. I have used Devcon products for decades in my work. The bond strength and quality are second to none for me. The Apoxie Scult my wife has used for jewelry making and one night as I was cursing at the mess I was making with a cheaper epoxy, she brought that out. What a difference it made. I still use Devcon if I am backing a lot of pieces, I mix it and spread it out on wax paper thinly and then press in the cabs.
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…And the Apoxie can be ground/sanded/polished along with the stone? That was one of the things I have to consider…
And thanks for the testimonial… it helps to have an actual user report on their findings.
They both can be ground and sanded, equally well.
I have just started grinding cabs, but have been backing stones for my wife for awhile. I am hoping to be able to do much more as I find it very relaxing. Unfortunately my work takes me away from home quite a bit. My son came over this weekend and we cabbed some Opal and Lapis. I have about thirty pieces of turquoise backed. Now I need to put them on dopping sticks so I can grind them next weekend.
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Excellent! Good to know. I just picked up some Number 8 Mine turq, really pretty in the matrix, but, oh my! they are thin slices.
And of course, I still have a lot of the baby blue pieces from my dad’s collection that will need some backing to be useful.
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Nice looking pieces. The backing not only strengthens the piece for grinding, it helps raise thin cabs to sit up higher in the mount, plus it acts as a shock absorber if you accidentally bang the stone on something. Did you get a cabbing machine yet, or join a gem club?
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The backing will also help flatten out any wedge shaped pieces so you won’t have to grind away so much material.
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Not yet. Waiting for both until after we move (hopefully, sometime this year). In the meantime, I am using sandpaper and a mini-Dremel on what I have: mostly prepping the pieces to a pre-form condition. So far, I’ve done a number of turquoise pieces, a few calcite, and one lapis. None are finished, by any means, just rough-shaped.
Top row is my current batch, bottom left are two pieces that were mostly chalk, but still okay for making into casual jewelry. I’ll use those as practice pieces once I start silver-smithing.
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Those look great! They are just right for backing, which is why you probably asked in the first place. The cabbing machine makes the grinding so much faster and less labor intensive. My next piece of equipment will be a flat lap. This will make flattening the bottom and preshaping so much easier.
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Watch John Hartman from Durango Silver on YouTube. He has a series of videos on turquoise cab cutting. He shows the whole process and gives a lot of good tips.
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Just watched the John Hartman video… great tips. Seeing him in action gave me deja vu from my time when my dad was teaching me. Some of the things were different then, since I learned all this over 40 years ago… new materials like Devcon, and such. But overall, the sequence is still the same as what I learned. Can’t wait to get my machine and workbench once we move!
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Hello Christibo instead of using devcon could I use a good epoxy putty
Worth a try I suppose.