eMax Internal Fit (White Powder)

[MushMaster]

Good day all,

Running into some pressed lithium disilicate issues lately and cannot quite put my finger on it.
Always made a DuraLay cap on which the wax design is made, invest, burnout, press, remove some reaction layer and beauty; both the press and the fit. Lately however, we noticed that the margins are not always fully complete and the internal area has gotten a white-ish layer that when removed with a diamond, comes out in the form of a white powder. This consequently also influences the internal fit and results in the decision to redo the case.

In the process of elimination we came up with the wax. We reverted back to a wax that used to be a success and it does not solve the issue. We have started using less separation liquid, thinking it would react with the investment material. Furnace is calibrated. Liquid is fresh. We are now going to try a few sample pieces and try a GC ingot instead of eMax to see if that makes a difference, because at this point we do nothing different from when it was not a problem.

Perhaps you have had the same issue and found the culprit, if so I would love to hear about it. Any ideas are welcome and if you want more information, I will get you the info and update this (first) post accordingly.

Thanks!

 

[CatamountRob]

If it were me, I’d start by eliminating the duralay layer and see what happens.

 

[Car 54]

Some bad investment, investment breakdown?

Are you set up for design and mill? From some of your posts you seem to be. Why aren't you milling them?
Milled wax is really nice to work with. I haven't used Duralay for any normal crown and bridge
units since the 90s? Do all of my emax in milled wax, comes out wonderful, along with Microstar investment.

 

[Affinity]

Pattern not burned out enough, run up to 900c for 15 min. The margins are the tell-tale sign because they are the last portion to be burnt out. Although you didnt really list any specifics of your burnout temp (burnout calibrated or press?),investment, acid? The GC ingot will press different because it doesnt have a reaction layer on it like emax. If you still have it with the GC, then you know youre either not high enough on burnout or pressing too hard, too hot or too long.

 

[ztech]

I have to agree with bad investment. Your margins are most vulnerable to investment breakdown since they are the first to heat up and will be in the hottest area of the mold for the longest so they will show the slightest problem with investment.

 

[charles007]

White powder is not emax... lol, dump the investments. Kind of surprised Duralay is still on the market.. Last time I used Duralay was for np Maryland bridges and stopped making them 6 months later,... that was in the early 80's I guess ? lol
Microstar worked great for me on max, pfm and cast gold crs.

 

[Affinity]

'White powder' could describe the reaction layer, or the investment breaking down. You could have reaction layer without investment breakdown, or you could have both. They kind of go hand in hand based on all the other factors that go into pressing, mainly heat.

 

[FASTFNGR]

Good day all,

Running into some pressed lithium disilicate issues lately and cannot quite put my finger on it.
Always made a DuraLay cap on which the wax design is made, invest, burnout, press, remove some reaction layer and beauty; both the press and the fit. Lately however, we noticed that the margins are not always fully complete and the internal area has gotten a white-ish layer that when removed with a diamond, comes out in the form of a white powder. This consequently also influences the internal fit and results in the decision to redo the case.

In the process of elimination we came up with the wax. We reverted back to a wax that used to be a success and it does not solve the issue. We have started using less separation liquid, thinking it would react with the investment material. Furnace is calibrated. Liquid is fresh. We are now going to try a few sample pieces and try a GC ingot instead of eMax to see if that makes a difference, because at this point we do nothing different from when it was not a problem.

Perhaps you have had the same issue and found the culprit, if so I would love to hear about it. Any ideas are welcome and if you want more information, I will get you the info and update this (first) post accordingly.

Thanks!

Forget the Duralay and start from there. Check liquid ratio to powder, check powder humidity and bags integrity, short margins could be not enough pressing time or not enough temp. After all check what changed from previous good presses and go back to it step by step.

 

[Darren S]

Instead of Duralay, use Pi-Ku-Plast from Bredent. Burns out cleanly and collapses in on itself instead of expanding. Or stick with an organic wax.

 

[MushMaster]

Sorry for the late response. We found the culprit and are back to great results. The problem was non of the materials, but somehow the furnace has been off. The pre-programmed program was too hot, even when calibrated. We reduced the temperature with 10 degrees and there is close to no reaction layer.

As for Duralay haha, yes it is still around and we still use it. It has been great. As far as we know it too burns out clean and has come to aid in making little matrixes/keys as well. I will have a look at Pi-Ku-Plast Darren, sounds like something we'd be interested in. I know some of you may raise and eyebrow at these techniques so 1982, but in some cases the old still hold true in the new.

Thanks all!