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[Ryaly2dogs]

Good morning:  I attached a photo of a preform and another in middle of 500 grit to frame a question on a Plasma agate sphere (collected from Clear Creek, CA)I am in the middle of.  I originally thought I could grind past such flaws as shown but I am running out of diameter!  Other portions of the sphere have smaller holes/voids.  At present I am resolved to stop further grinding and start finishing the current 2.7" diameter sphere, and need to have a plan to use a filler agent.

My question is thus, is epoxy a viable solution or is this a job for Opticon, and at what stage in the grind polish is it best to apply?  Could use some advice here, so I can make a good next decision.

Thank you in advance.

[Jhon P]

If I don’t like the flaws I will sand to 200 grit and use bond optic. It dosent take a lot I will wrap it in Walmart brand plastic wrap. A good sister piece a couple of layers. Set the balk in the middle and apply the mixed bond optic wrap it in the plastic and you can move the epoxy around and get it to soak into all of the voids and cracks. It takes a long time to set up so you can check it and move the epoxy around. I hope this makes since.

[Ryaly2dogs]

Thanks; I think I  am getting the picture, rather ingenious I must say.  Use a disposable plastic wrapper to distribute sealer where needed around the sphere.  Is there a particular brand of bond optic you recommend?

thanks again.

[Sandsave]

Ditto here, I base mine on the material if it's got natural voids, vugs, etc. I don't try to make it something it's not, it's just part of the rock. I'll use it when there's a fracture that is not part of the natural material.

[finegemdesigns]

It seems like the longer the cure time the less epoxies will yellow over time but I'm not a chemist.

For example Loctite 5 minute epoxy is great for dopping but bad for cabochon filling because it yellows quickly, maybe in as little as a month.

Epoxy 330 hardens rock solid in 12-24 hours. (I prefer to wait 24 hours)
Yellows but much longer time period maybe even years.

Hxtal - Super premium epoxy DOES NOT YELLOW. But cure time could be a week. Very expensive.

For your ball I would go with the Epoxy 330 since even if it does yellow eventually the color will blend with the ball's colors.

[Jhon P]

The bond optic is not supposed to yellow. It was designed for lapidary use to stabilize and fill voids and cracks. And is UV resistant. It will take 24hr to set up and two or three days to cure unless it is heated.
It’s like hyxtal but 1/3 the price. Still expensive about $50 for 12 oz but a little goes a long ways

[Jhon P]

I tried 330 epoxy, it worked good for the bigger cracks or holes but was too thick to soak into o the small fractures. I have had a couple of preforms break and I glued them back together with 330

[finegemdesigns]

I tried 330 epoxy, it worked good for the bigger cracks or holes but was too thick to soak into o the small fractures. I have had a couple of preforms break and I glued them back together with 330

You can thin the 330 by mixing it with acetone. This will allow it to penetrate easier into thin cracks.

[Ryaly2dogs]

Thanks for the thoughts.  330 Epoxy it is (which I have on hand which is a nice bonus), with a smidgeon of acetone.

[55fossil]

   330 epoxy will also thin out with heat. I put it under a light until it gets more like water than syrup. I do this to make doublets because it helps remove air bubbles and makes an excellent transparent bond.

When you thin with acetone does the 330 shrink as it dries out?

[Ryaly2dogs]

Good tip on adding the heat lamp; I will do that as well.  All sorts of great insights; thanks to you all.

[finegemdesigns]

   330 epoxy will also thin out with heat. I put it under a light until it gets more like water than syrup. I do this to make doublets because it helps remove air bubbles and makes an excellent transparent bond.

When you thin with acetone does the 330 shrink as it dries out?

Again I'm not a chemist but I think the acetone evaporates as the epoxy cures so what happens is the epoxy ends up the same as if the acetone was never added. The plus of adding it to start is that it penetrates cracks easier. Also it might take a bit longer for the epoxy/acetone mixture to cure. As far as shrinking I don't know since I've never used an epoxy/acetone mixture to fill a large hole. In this application you could do the process in 2 steps. Start with the thinner epoxy/acetone mixture (to fill thin cracks and seams) and then after that cures go to regular full strength epoxy 330 to fill the larger holes and gaps remaining.

[lapidaryrough]

   after the sphere has been coated in optic put in long plastic bag. In the corner of the bag re-coat sphere, Spin bag tight around the sphere in long bag. put it in deep water.  5 gallon bucket. Should be about .55 Lbs. of pressure on sphere to  push the air bubbles out  /  and to the surface to grind off.

  Jack

[Jhon P]

Hey Jack, that sounds like a great idea. I will try it on the next sphere that I need to stabilize. I have an Apache Gold that is In The schedule that I think will need it.  Was this your idea?