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Post by Psycho on Nov 7, 2017 15:29:35 GMT -5
Is there a preferred material for backing cabs? I have a lot of slate from Alaska that was given to me and I know it's rather soft but it it acceptable for backing or is it too soft? Thanks for the help
Frank
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Post by rockjunquie on Nov 7, 2017 16:45:13 GMT -5
I'm sure others will have a better answer, but I know a guy (bikerRandy) who uses plate glass and it works for him. Glass has to be softer and more brittle than slate.
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Post by Bluesky78987 on Nov 8, 2017 10:01:45 GMT -5
You can use anything you want! In fact, the softer the material, the better, becuase then you can easily grind it as thin as you want it (rather than having to worry about cutting micro thin slabs of the backing material). I've used howlite a lot, for the white color behind a clear cab (like rose quartz or graveyard point), or black obsidian. Basanite is popular as a soft black material, but you could use anything you wanted.
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zarguy
fully equipped rock polisher
Cedar City, Utah - rockhound heaven!
Member since December 2005
Posts: 1,791
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Post by zarguy on Nov 8, 2017 10:19:42 GMT -5
For Turquoise, many people use Devcon epoxy or JB Weld. I don't like to have black backing on my Turquoise cabs, so I started crushing Turquoise matrix (I have some Royston, which has lots of matrix) and mixing it with epoxy. You could crush anything that has the color you want. Lynn
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Post by Bluesky78987 on Nov 8, 2017 10:30:32 GMT -5
Yeah, as zarguy says, the other method is to use some sort of goupy mixture, blob it on wax paper, and push your stone down into it. You coul just use straight epoxy too, but that would look wierd.
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Post by Psycho on Nov 8, 2017 11:17:25 GMT -5
Makes perfect sense to me now lol. So the slate could be used with a darker Jasper possibly then or whatever need be.
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Post by Pat on Nov 8, 2017 11:58:00 GMT -5
....and I was going to say we usually use sterling or a stepped bezel!
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Tommy
Administrator
Member since January 2013
Posts: 12,684
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Post by Tommy on Nov 8, 2017 12:21:53 GMT -5
Good thread! I've already learned a few new things. I've only done a couple of backed cabs but the most recent on was on a super thin piece of Woodward Ranch agate I got from Jeremy riverbendlapidary. I wanted a clear backing and I've searched and tried various solutions including a couple different types of glass (NEVER again! lol) and clear quartz - nothing was working for me. In a classic duh moment I remembered that I have some big chunks of very low quality Graveyard Point plume agate in which wide swaths of the middle are almost completely clear and generally devoid of plumes. So after slicing it very thin I used it as a backer on this piece and I'm very pleased with how it turned out. The backer is not completely clear but it's fine and doesn't add or detract from the front as far as I can tell.
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Post by rockjunquie on Nov 8, 2017 12:28:02 GMT -5
Good thread! I've already learned a few new things. I've only done a couple of backed cabs but the most recent on was on a super thin piece of Woodward Ranch agate I got from Jeremy riverbendlapidary . I wanted a clear backing and I've searched and tried various solutions including a couple different types of glass (NEVER again! lol) and clear quartz - nothing was working for me. In a classic duh moment I remembered that I have some big chunks of very low quality Graveyard Point plume agate in which wide swaths of the middle are almost completely clear and generally devoid of plumes. So after slicing it very thin I used it as a backer on this piece and I'm very pleased with how it turned out. The backer is not completely clear but it's fine and doesn't add or detract from the front as far as I can tell. drooling WOW! What a cab! Great save Tommy! I have some charoite I need to back. I have never backed anything.
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Post by Psycho on Nov 8, 2017 12:28:32 GMT -5
Looks good to me Tommy
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Post by gmitch067 on Nov 8, 2017 16:45:25 GMT -5
I used Starbond Thick CA epoxy to create a firm backing to work a few cuts of Malachite which would have broken as I hand cabbed them. I cut some clear plastic pieces - same material and thickness as a plastic water bottle but without the ribbing (it was actually the plastic packaging the Starbond was shipped in). I laid the glue on thick to both the top of the plastic and bottom of the 30x40mm oval cab cutout - then rested the stone on top (lightly... no squishy... wanted it thick). I did NOT use accelerator to quick dry the glue, because it would generate uneven ripples as the catalyst reaction works through the bed of glue. After it dried I proceeded to grind and polish the stone - leaving the plastic in place. After the stone was polished, I pried the plastic off the Starbond using a razor knife... leaving the CA glue base. I like Lynn's zarguy method of using grindings mixed into the epoxy. I will try that in the future.
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Post by rockjunquie on Nov 8, 2017 17:25:30 GMT -5
I used Starbond Thick CA epoxy to create a firm backing to work a few cuts of Malachite which would have broken as I hand cabbed them. I cut some clear plastic pieces - same material and thickness as a plastic water bottle but without the ribbing (it was actually the plastic packaging the Starbond was shipped in). I laid the glue on thick to both the top of the plastic and bottom of the 30x40mm oval cab cutout - then rested the stone on top (lightly... no squishy... wanted it thick). I did NOT use accelerator to quick dry the glue, because it would generate uneven ripples as the catalyst reaction works through the bed of glue. After it dried I proceeded to grind and polish the stone - leaving the plastic in place. After the stone was polished, I pried the plastic off the Starbond using a razor knife... leaving the CA glue base. I like Lynn's zarguy method of using grindings mixed into the epoxy. I will try that in the future. Interesting. Haven't heard that before. Did the base dry flat and not crackled?
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Post by gmitch067 on Nov 8, 2017 22:10:27 GMT -5
I used Starbond Thick CA epoxy to create a firm backing to work a few cuts of Malachite which would have broken as I hand cabbed them. I cut some clear plastic pieces - same material and thickness as a plastic water bottle but without the ribbing (it was actually the plastic packaging the Starbond was shipped in). I laid the glue on thick to both the top of the plastic and bottom of the 30x40mm oval cab cutout - then rested the stone on top (lightly... no squishy... wanted it thick). I did NOT use accelerator to quick dry the glue, because it would generate uneven ripples as the catalyst reaction works through the bed of glue. After it dried I proceeded to grind and polish the stone - leaving the plastic in place. After the stone was polished, I pried the plastic off the Starbond using a razor knife... leaving the CA glue base. I like Lynn's zarguy method of using grindings mixed into the epoxy. I will try that in the future. Interesting. Haven't heard that before. Did the base dry flat and not crackled? I did not notice any cracking in the flow of Starbond CA glue when it dried. It was about 1/16" in depth and clear. It did have a few bubbles, but with a stone that is not transparent, I did not think it important. The plastic piece was stiff enough to allow the base to be flat, and it looked fairly even in thickness throughout.
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Post by Psycho on Nov 8, 2017 22:33:11 GMT -5
Lynn When you use the grinding method how fine is the grinding to keep the epoxy mixture even and flat ?
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Post by gmitch067 on Nov 8, 2017 23:01:02 GMT -5
I do not really touch the base with the dremel grinder other than to go around the edges to make the plastic shape adhere to the outline of the cab. The flatness of the base comes from the stiffness of the plastic piece... the 30x40mm oval cab is small enough so that any waviness is minimal to non existent.
The Starbond Thick Gel CA glue does not bond to the plastic permanently... but it does bond enough to keep it in place as I manipulate the cab around the wet/dry silicon carbide sand papers without peeling off or becoming mush in the puddle of water. The plastic protects the base from scratches. When I peel it off at the end, the base looks flat and nice and shiny (with a few internal bubbles in the epoxy).
Oooops... Sorry... thought the question was for me. Sorry Lynn!
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Post by Psycho on Nov 9, 2017 7:21:35 GMT -5
Lol but you gave me some additional information.im new to all of this so I will take what I can get lol
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bitterbrook
noticing nice landscape pebbles
Always remember STEP NUMBER ONE!
Member since September 2006
Posts: 99
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Post by bitterbrook on Nov 10, 2017 8:16:57 GMT -5
Ideally, I will use the same material, front & back. When that isn't possible I try to find something of a similar color.
In class, I'll grab whatever is closest for a class demo; I've come up with some "interesting" cabs that way. I demonstrate putting a dome on the front part without cutting into the back piece, leaving an eentsy-weentsy girdle around the front piece. If you cut into the back piece, the cab is flawed (my opinion) because you can see the back piece when looking at it from the front.
I have some Ocean Jasper slabs with long veins of open drusy, which would make an unstable cabs if not backed.
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zarguy
fully equipped rock polisher
Cedar City, Utah - rockhound heaven!
Member since December 2005
Posts: 1,791
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Post by zarguy on Nov 10, 2017 10:41:08 GMT -5
Lynn When you use the grinding method how fine is the grinding to keep the epoxy mixture even and flat ? I crush the matrix, I don'r grind it. It crushes down to a fine sand. I make a dam out of masking tape and form it around the cab, fill it in with the mix & then grind the back flat after it hardens. I know, pictures would help. I may have time to shoot some on Saturday. I haven't yet made a large enough quantity to spread on waxed paper & set the cabs/preforms into like people do with JB Weld. I hope to experiment with that method though. Lynn
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Post by Psycho on Nov 10, 2017 11:00:29 GMT -5
Thanks for the ideas and info Lynn
Frank
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Post by rockjunquie on Nov 10, 2017 11:21:20 GMT -5
Great thread, y'all!
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