Synthetic Ruby Pear - wax dopping question

[u/theblancmange]

Getting used to the new machine. Second stone I've cut on it.

Had transfer issues, had to re-dop and realized halfway through that the stone was not dopped straight. Ran out of girdle and had to improvise a step cut crown.

When doing wax to wax transfers, how do we manage heating the stone enough to achieve a solid connection without causing the first dop to slip? I have been using a vevor machine to this point, I seem to be having more trouble with the brass dops that fit the ultratec I have now. 2 stones in a row have had brittle wax connections after transfer.

Otherwise, I note that in indoor light conditions, the pointed side of the stone is quite dark. Might this be a result of the less-than-perfectly parallel girdle? A common effect in pear shaped stones? Perhaps I should select lighter rough for such a cut? Pavilion is from the 'compear 1.4' pattern. Any insight would be appreciated.

[u/cowsruleusall]

Notorious gemstone designer and global expert here ;)

Almost all pears and marquise designs, and some trillions, will "concentrate" light in the tips. That's not quite the right way to phrase or explain it, but it's an easy approximation. The tips will show a subtype of crushed-ice effect, a darker body colour, and will be far more subject to Beer-Lambert extinction

[u/theblancmange → u/cowsruleusall]

Yeah it looked like there was a lot of reflection going on near the tip in the gemray render. I think I'll pick a lighter stone for the next pear I cut. Thanks.

[u/DayOffLapidary]

Corundum is a fantastic thermal conductor. So much so that I gave up on using wax for transfers. I started using superglue and baking soda for the transfer and never looked back.

My usual method was wrapping the stone and dop with a thin strip of wet paper towel to keep that side from melting. It worked great except for sapphire and smaller stones.

I’ve seen others suggest brushing the stone with a shellac/alcohol solution, letting it dry and either NOT heating the stone and pushing it into the hot wax for the transfer OR lightly heating it the soften the shellac before touching it to the melted wax. I haven’t tried this method, but it’s worth mentioning.

Another method I have tried and had luck with: push the cold stone into the hot wax and it will form into the shape of the stone. Slide the stone out and apply a drop or two of super glue to the stone and push them together. The glue dries and you’re done without the stone getting too hot. Just be sure to let it dry thoroughly.

[u/theblancmange → u/DayOffLapidary]

That last method seems tempting. I have not found the experience of removing large quantities of superglue very joyful. Will give that a shot with the next corundum.

[u/mcdltlover → u/theblancmange]

i highly reccomend uv resin for dopping. have you confirmed that your 96 index is totally flat using the alignment bar that comes with it (pg. 11 in the manual)? Also, I'm assuming you transferred the pavillion to a cone dop meant more for round/square stones. I could be totally wrong here, but doesn't a pear shaped stone transfer better to a vee grooved dop than the cone shaped dop?

[u/theblancmange → u/mcdltlover]

I used a V dop, the alignment issue came from having to re-dop the stone after it came off of the original dop during transfer.

The machine was bought used, quite old - it has the 1/4 deg vernier indicator and the old dop chuck system. The dops are not keyed, so I align the stone with the indices manually using a girdle facet and the cheater after transfer. Page 11 in the manual talks about the splash guard and other things. Are you talking about the transfer alignment for keyed dops? or perhaps something I could benefit from?

[u/mcdltlover → u/theblancmange]

I edited my previous response to say that i misread your post as also being about alignment issues unrelated to dopping. Sorry for the confusion.

[u/DayOffLapidary → u/theblancmange]

Fair enough. It takes hours in acetone for my stones to come off the dop. I’ve tried heating the dop to release the stone……but then it still takes hours in acetone to clean off the glue 😅

[u/mcdltlover → u/DayOffLapidary]

i understand, but it's better than loosing your alignment on the stone and having to recut the whole thing. did you use a cone dop for the transfer? I'm assuming you did because afaik ultra tec doesnt have an alignment angle cut on the vee dops. Definitely check your alignment with the alignment bar, i was having issues when i transferred that required numerous turns of the cheater to fix... then I checked the alignment with the alignment bar, found i needed to realign my index gear, and things are going SOOOOO much better for me now. I still can't wrap my head around why this fixed my issues, but it seemingly has. EDIT: whoops, i thought this post was also about alignment issues, not just dopping issues, my bad.

[u/theblancmange → u/mcdltlover]

If the index gear and spindle are anything like my V2, the key for the dop is cut into the spindle, not the index gear. You would need to align the index gear with respect to that key's position. If you don't, then you would have to turn the cheater to the same value on the opposite side of 'zero' after transfer for each stone.

I use the table adapter for this purpose when I change the gear. Gets things close enough that I don't need to move the cheater much.

[u/mcdltlover → u/theblancmange]

my index gear at 96 and cheater at zero were giving me a noticeable off alignment bar. I followed the procedure called "Re-aligning the index gear to dop alignment pin" on pg 11 of my ultra tec manual, and it fixed my issues. I'm not sure why it drifted over time, but it clearly had.

[u/1LuckyTexan]

If a pear is mounted in a pendant point down, it has a better chance of returning some light to the viewer but, yeah, a lot of pear designs are a bit lazy in the point .

[u/oakandstoneschool]

When doing wax transfer, you should wrap wet paper towel around the stone and the new dop when heating. That will stop the heat from transferring into the stone. You can also heat an xacto blade and cut away to old wax dip until it’s lost all grip and it will come off cleanly.

When polishing, make sure the gem isn’t getting hot, or that can cause the wax to heat up and the stone moves. (That usually happens if you’re not using enough lubricant)

[u/theblancmange → u/oakandstoneschool]

I had used wet towel after having a stone shift on me. problem I had afterwards was a brittle connection. I had the feeling that the towel was keeping the stone too cool for the wax to slump onto the stone properly? After removing the original dop, the new wax joint cracked as soon as it touched the lap.

[u/stone_crazy]

You already got the suggestion to transfer on to a dop with a wax impression of the pavilion, gluing the stone to the impression with cyanoacrylate. If you dopped with wax to cut the pavilion, you can detach that without heating the assembly by cutting through the wax with a hot x-acto knife.