Aussie Lapidary Forum

LAPIDARY => Cabbing and More => Topic started by: tinker on July 29, 2021, 02:45:45 PM

Title: Opal doublet backing.
Post by: tinker on July 29, 2021, 02:45:45 PM
I hope this is the right section, I have a lot of crystal opal and was intending of making doublets out of the samples.  Can anybody tell me what I can use as the backing material, or where I can get material to make doublets.
Title: Re: Opal doublet backing.
Post by: Bucket on July 29, 2021, 05:42:56 PM
Some have used a type of black glass which can be purchased separately, it's thin and easy to use. I've successfully used black jasper, sliced as thin as I could, then ground away more if need after the opal is attached. For more accurate cutting I used a 6 inch very thin saw blade. I know some others have used other material, but I have good, very black jasper which does the job for me.
Title: Re: Opal doublet backing.
Post by: tinker on July 30, 2021, 11:40:21 AM
Thanks Bucket,   I've got a bit of almost black Jasper I will give that a try, what about black potch.
Title: Re: Opal doublet backing.
Post by: Rusted on July 30, 2021, 11:42:10 AM
Black Jasper is what I have used too. I have seen black Radiator putty used. Not my cup of tea but it did work. I think the stuff is sodium silicate so it sets hard.
Title: Re: Opal doublet backing.
Post by: Bucket on July 31, 2021, 03:03:02 PM
I think black potch would work well, they used to use that to be more 'genuine' 40 - 50 years ago.
Title: Re: Opal doublet backing.
Post by: steveo on August 02, 2021, 04:19:37 AM
Some use old vinyl records and probably smooth back after gluing.
Title: Re: Opal doublet backing.
Post by: MakkyBrown on August 02, 2021, 08:13:51 AM
I've heard of black obsidian being used. Might have picked that info up watching Outback Opal Hunters :)

MB
Title: Re: Opal doublet backing.
Post by: mehoose on July 28, 2022, 10:11:38 AM
tinker, I've also seen a vid where they spray the back of the opal slice with black paint first and then glue onto the backing. (possibly to hide glue if that changed colour over time?)I seriously cannot recommend that either way because that would introduce a possible secondary breakdown. How long would the paint integrity last? 
Just mentioning it because at the time that seemed acceptable and then would it matter a toss as to what colour the backing is. hmmm.
Title: Re: Opal doublet backing.
Post by: dom105 on July 28, 2022, 05:56:48 PM
Sorry to stick my nose in, but I'd like to know what is the thinnest opal that can be turned into a doublet.
Also if you happen to have black potch, wouldn't it look more natural than glass or obsidian?
Title: Re: Opal doublet backing.
Post by: mehoose on July 29, 2022, 11:28:28 AM
Well there's plenty of potch around Dom. Maybe because the slivers are getting so darn thin they're going for stronger backings these days.

I just had a quick measure of the 3 doublets I have here.
10 X 8~ 2.5mm depth overall, flat top and back with rounded edges, 1/3 opal~2/3 backing.
9 x 7~ 2.5mm depth overall, flat top and back with rounded edges, 1/3 opal~2/3 backing.
I'd say the above two were done at the same time because of the backing colour and overall shape.

9 x 7~ 3mm depth overall, more a domed top and domed backing, slightly greyer backing, again a 1/3, 2/3 split.

Which is more visually pleasing face up? They both look good to me.
As a jeweller, I'd prefer the back shape of the first two and probably the domed top of the last one. :)

I did set one for my mother in a pendant and it was the same as the first two, flatter. I would have welcomed a more domed top for the bezel setting.
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