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Removing adhesive from lapis cabochon


#1

Can anyone recommend how to remove old adhesive from lapis lazuli without damaging the stone?

A customer brought me a rather large lapis cabochon that had fallen out of its original setting. The stone isn’t a particularly high quality specimen, but it was a gift from the costumer’s brother, who purchased it in Afghanistan. The customer would like me to create a new setting that would allow the back of the stone to be visible.

Here’s my dilemma: the original setting was cast and the stone was set using some type of adhesive, which the original maker applied quite liberally. Can anyone recommend a way to safely remove the old adhesive from the back of the stone? I know lapis is soft and porous, so I’m reluctant to use solvents.

Thank you,
Renee Ziegler


#2

Assuming that the adhesive isn’t holding the stone together, treat it like a lapidary project and cut and polish back to the original stone surface. Lapis is soft. Assuming that the back is flat, this should be pretty easy to do…Rob


#3

While totally recutting and repolishing the stone would doubtless work, if Renee had the proper lapidary equipment, that should be a last resort. Before doing that, I’d suggest soaking the stone in a solvent such as “Attack” EAIaIQobChMIrvS96aL44AIVnCCtBh1ZOgVEEAQYAyABEgKvC_D_BwE which will loosen epoxies and some other glues. Use it with caution, since the fumes are nasty and you don’t want it on your skin either. It shouldn’t damage the stone, although if you notice the solvent turning blue, that will be dye coming out of a doctored piece of lapis.


#4

Wouldn’t someone who makes jewelry have some sort of lapidary capacity before they had a bottle of “attack”? I am thinking progressively finer sheets of abrasive paper and possibly Zam for a polish; especially for the back only of a soft stone like Lapis. This is an honest question. In addition to making lots of jewelry, I have a well equipped lapidary shop and work a lot of Lapis, but I have no bottle of attack in my shop. I am not even sure what I would do with it…Rob


#5

I have used attack and acetone but would not do so with lapis, pearls or any other porous material. My preferred method where it will work is to boil item in water to soften adhesive which then is usually soften enough to remove.

Hope this helps
Franz on the coast of central California where it is still raining


#6

Franz, I will try that! I did try denatured alcohol on a cotton swab to see if the adhesive would soften just a bit and it had no effect whatsoever and I was reluctant to to use anything stronger.

In response to awerby, I have asthma so I avoid using most solvents if possible and when unavoidable, I take things outside. Since it’s still winter here in central Pennsylvania, I can’t really work outside yet.

Thank you all for generous suggestions–I really appreciate it!
Renee


#7

Rob, I have abrasive paper and Zam on hand! Unfortunately I don’t have lapidary equipment (unless you count an antique lap saw that my husband purchased at an auction: it has no safety features and the power cord looks like a fire hazard waiting to happen).


#8

My thought was to try it by hand placing the paper on a hard surface, wetting it, and then seeing if you could grind through the glue and begin working the Lapis to the point where you could polish it with Zam. Zam works well on Turquoise just using your polishing wheel. Lapis is soft and it might work for Lapis as well. Others may know the answer to this question, but I will try later to see if it works on a piece of scrap Lapis. Since you are working on the back, it doesn’t need to be as well polished as the front. Another thought is to do a search in your area for a local Rock and Mineral club to see if you could contact someone who would be willing to do this for you. Where in Central PA are you?..Rob


#9

This piece was sanded on the right side up to 1200 grit and then polished on a cotton wheel with Zam. It isn’t a great polish, but then again Lapis is soft and doesn’t easily take a high polish. I think that your best bet is to find someone with lapidary equipment to do the job for you. Good luck…Rob


#10

I live in State College, PA. I know there’s a local rockhound group in the area because they used to host a geode party for kids in the basement of the geology department. Someone in that group must do lapidary work, or will know someone local who does. If I can’t find a contact online, I’ll email the geology department.

If all else fails, I have lots of experience sanding. I like the soft polish on your example and I’m pretty sure my client will be fine that, too.

If I can’t remove all of the adhesive stain, I’ll design the fretwork on the backplate so that it doesn’t show.

Thank you again for the great advice!


#11

Small world, our son and his family lived in State College up until last summer when they moved back to DC. We would visit from near Syracuse on a regular basis. There is a nice coal themed museum at Penn State. You should be able to find resources there. There is also a great jewelry store right on the corner of College and Allen named Moyers. They may be able to help. A quick look on the internet list the following:

https://www.nittanymineral.org/

Take a look and give them a try. Good luck…Rob