QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on May 28, 2018 3:51:51 GMT -5
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Post by opalpyrexia on May 28, 2018 11:14:29 GMT -5
Whoa! That site has some interesting videos with top grade rough opal, with most of it appearing to be crystal. Thanks.
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Post by Rockoonz on May 28, 2018 13:28:39 GMT -5
Definitely works some top end material and does a fine job, but..., Dopping opal with wax? Sorry, had to say it, introducing heat to opals is the kiss of death.
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timloco
has rocks in the head
Member since April 2012
Posts: 545
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Post by timloco on May 28, 2018 14:59:02 GMT -5
Looks great! I've been dopping mine with wax, it hasn't seemed to hurt it yet. I usually use double sided mounting tape but for some reason it doesn't stick well to opal so I went back to wax for it.
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Post by opalpyrexia on May 28, 2018 15:26:47 GMT -5
Dopping opal with wax? Sorry, had to say it, introducing heat to opals is the kiss of death. I've been dopping mine with wax, it hasn't seemed to hurt it yet. I use Loctite 454 epoxy and brass rods, but just because I don't like wax. To remove an opal I heat the brass rod with butane torch a short distance from the opal until it comes off easily. Sometimes the very small opals get quite warm or even hot to the touch if I'm too slow, but I've never had one damaged by the heat. Heat transfer to the opal is slow enough that thermal shock hasn't occurred for me. I would think that wax dopping would be similar.
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Post by Rockoonz on May 29, 2018 1:07:33 GMT -5
I dop most things with cheap HF epoxy on aluminum dops, and het the rod to release, holding the cab with a wet rag so neither of us gets too hot. I'm also beginning to use the carpet tape too. Since most of my opals are backed or triplets heat can also cause problems with the 303 epoxy I make them with, along with the intarsia pieces I also like to make. I don't like wax either, doesn't stick well enough for me, especially in cold humid weather like about 2/3 of our year. To get it to stick well I've always had to heat up the stone enough so it sheets onto it. Might not affect what the opal looks like today, but opals, once they're released from the dirt, aren't going to have that flash forever, UV light and heat will see to that. Probably overly anal retentive.
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gemfeller
Cave Dweller
Member since June 2011
Posts: 4,019
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Post by gemfeller on May 29, 2018 1:12:37 GMT -5
Definitely works some top end material and does a fine job, but..., Dopping opal with wax? Sorry, had to say it, introducing heat to opals is the kiss of death. I've dopped Australian opals with wax for 40 years and have never lost a stone. It's all in the way they're heated. Rapid heating crazes opal but slow, gently increasing heat doesn't. I use a dop station heated by a 100-watt light bulb and start the process at room temperature.
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Post by opalpyrexia on May 29, 2018 9:19:21 GMT -5
I'm also beginning to use the carpet tape too. For larger stones I assume. What diameter dops do you use with the tape, and do you twist the finished cabs to remove them?
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Post by Rockoonz on May 29, 2018 16:35:00 GMT -5
I'm also beginning to use the carpet tape too. For larger stones I assume. What diameter dops do you use with the tape, and do you twist the finished cabs to remove them?
I think the first time I tried it was on a triplet in Pat Lloyds class at the rockhound retreat about 5 or so years ago. Probably about a 6x9m free form cab on a nail with a washer epoxied to it. Most recently it was roughly a 13x18 fossil coral cab on an aluminum dop I turned on my lathe at work. Since the tape is a bit cushioned larger cabs wiggle too much for my taste.
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Post by Rockoonz on May 29, 2018 16:36:53 GMT -5
Yes, twist and pry to remove, and tape rolls right off.
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