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Question on hybrid dopping

Hello all, I have completed a few gems using just CA glue. But I have a few larger gems as well as a trillion where there will be gaps that I know will be too big to fill with just CA glue.

I have the Tom Herbst books and he suggests “bridging the gap” of leaving an impression in wax and then gluing to the impression. I tried searching here and on other forums for more info but nobody has given a description beyond that.

Whenever I try to leave the impression of the Pavillion in wax, the wax winds up pulling up with the gem as I remove it from the cone and I wind up with no impression and a mess. Any suggestions? I even tried leaving the gem in the fridge for a minute before attempting to ensure the wax wouldn’t stick to it (cheap lemon quartz no worries about thermal shock). If anyone has any suggestions to get this technique down it is much appreciated.

Thank you for taking the time time to read and answer.

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I use epoxy. I did hybrids before but had a few stones that moved if I used material that build up heat when polish. I never had any problems making the imprint. Is your wax crumbly?
I clean my stone with alcohol then apply some nail polish. Leave it for a couple of hours. Then I dop with epoxy. Let it cure for 12 hours. Leave it overnight in acetone when finished.

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Don’t fret! I quit using wax a year ago and wish I had earlier. Big stones are no problem with ZAP which tis a slightly different formula than regular CA. With a 12 mm dop set you can handle very large stones securely. One filling, second before contact, works for most. If there is a gap add a second application and a puff of accelerant helps. Leave it alone for a half hour. Alcohol is not enough to clean the stone and dops. Acetone is a must! There are lipids that do not dissolve in alcohol well especially skin oils. And FRESH acetone, never used for anything else, AND pristine, never handled pieces of paper towels. Sounds like a ritual and it is. No more failures is worth it.
To transfer your stone for the crown cutting let the dual dops with stone between them cure for a half hour. Then use you insulated dop holder on the dop you want to release. Using an alcohol lap hold the dop in the tip of the flame for a half minute for a 6 mm dop, more for the 12 mm dop and very quickly for the 2-3 mm dops.
When you are done and aim to remove the finished stone, put the dop in the holder and apply heat. Test it every 10 to 15 second with a dry piece of paper towel and see when it releases. Really big stone, like 50 to <100 ct. can take up to a minute or more and the glue goes soft. Let the stone cool by itself. Don’t cool it quickly.
I alloys forgot Tom Hebst advice for transfer, Wrap the stone you want to retain on its dop: cut a 3 inch strip, ¼ inch wide from a clean piece of paper towel. Wet it with a spray bottle and with tweezer wrap it around the shoulder of the gem. This takes practice. All this falderal may seem excessive, but as I said, it works! You will develop your own variation. Again the caution, skin oils from your fingers are evil and are the major cause of failures AND forget alcohol and use acetone always.
One last comment: I hope you have been introduced to the Guiui Dopper from Ultra Tee. Marvelous device for dopping the table end. More of that I you want.

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I think the replies so far are all absolutely fine and will work. It’s down to personal experience really. My preferred method is to use for the pavilion cut a sandwich of gem, CA, paxolin (the raw material for circuit boards available on line and cheap), CA, dop. It works really well. If a very big stone you may want to add additional support from epoxy. For the crown cut I use Epoxy. To separate the first dop after transfer, simply use a thin hacksaw to cut through the paxolin. Controversially I use dichloromethane to breakdown the epoxy. I know some would decry this but if used sensibly then I’m happy to use it. I actually keep it in a kilner jar under a layer of water.
Hope this helps.

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Awesome thank you all for the info!

For the guys using epoxy, I’ve read many places that acetone does nothing on the epoxy for release? I ordered some of the devcon 5 minute epoxy and I’ll likely try that once it comes and see how I like it. Do you recommend Vaseline or anything special on the culet to prevent chipping on release?

Britchie- Thank you I will look into the ZAP glue. I am already super meticulous about cleaning before during and after dopping as well as all throughout cutting so no worries on that front! I’ve seen the guiui dops, I’m not cutting anything more expensive than $5-10/ct so that extreme of accuracy isn’t needed yet. I’m using the magdop at the moment and it’s been working great.

Thank you guys all for your responses! I’ve actually managed to work out the wax/CA method since originally posting. I’ll be cutting two crowns today with this. If the wax doesn’t shift I’ll probably stick to this for a bit but I’ve got some epoxy on the way to see what I like best.

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I use normal 5 minute epoxy and acetone melts if fineover night. Because I uses a base nail polish on the stone it releases pretty quick.

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Having read the preceding comments regarding dop wax vs. glue, I have a curious question. What type of wax are you refering to, Green, Red, Black or Grey that you are having difficulty with in adhering to a stone? Secondly, what lap speeds are you using?
I use several different faceting machines when cutting stones Ultra Tec, Facette Gem Master and Prismatic, and most of the time I am running under 1000 rpm, especially when polishing. That is why I don’t understand the heat generation problem.
I cut as many as 15 stones a week and they range in hardness from 9 to 4.5 and range in size from 1mm to 30 mm and I do not have a problem with adhesion I use mostly black wax, but on rare occasions I will use red.
The only time I use CA, is when I am cabbing small stones too small to hold with my fingers 4x6 or smaller.
.

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I have used CA for more than 20 years and I have never had a problem with gaps. Go to your local Home Depot or Lowe’s and buy and you will find Loctite super glues in various viscosities from very thin to thick and various cure times (immediate to slow (30 seconds or so). I faceted a blue topaz of 20cts or so with 200 facets using Loctite CA glues. Because of a move and other events. It was glued to the dop for some 8 or 9 years in a drawer and when I could continue it I put the dopped stone in my Ultratec and completed the stone (including a transfer from pavilion to crown with no problem. Love those Loctite products. HTH Hank

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Glad you have solved your hybrid dopping problem. Yes, it is true that stones can shift when wax is involved, but the same can occur with epoxy from what I have heard. If you are reasonably careful not to build up heat and perhaps wrap the stone and dop with a wet paper towel when heat is a problem, you should be OK. Part of not building up heat is polishing quickly, which is down to a proper pre-polish and a good polishing lap. The newer polishing laps by Gearloose and Lightning Laps play a part in this. Using a two ring lap, pre-polish and polish, can help with getting registration right on polish. It is probably extended polishing, when subsurface scratches are there or the facet is not initially face on to the lap, that causes heat buildup.

As far as wax sticking to the stone, for anyone who has this problem, if the wax is only heated enough to make it soft enough to take an impression, and the stone is not heated, there shouldn’t be a problem. Use a high temp black or red wax. Make sure the stone is clean before applying the CA glue to the stone and wax.

Hybrid dopping solves the problem of defective wax joints due to not heating enough or burning wax, etc. Also, should the joint fail, you will be left with a jagged wax edge which will fit back together with the application of more CA glue exactly in registration, so that you can resume cutting as if there were no fall-off. It’s a relatively quick process and the stone is easy to remove and clean when cutting is done. No curing or excessive heating to get epoxy off. What’s not to like? -royjohn

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It’s been good reading all these comments too, I’ve learned quite a bit myself.
When I first started, I used wax and was advised to coat the pavilion in a dilute mixture of alcohol and shellac to give a better bond. It seemed to work, but constantly burning my fingers on the wax made me go down the CA route - not looked back.
For the epoxy, when I use a cone or vee dop I place a small bit of blue tack in the bottom just to cover the culet to protect it.

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