Bubbling in Vita VMK Master opaque! *PICTURES

[charles hallam cdt]

Have you been using this alloy and porc/opaque combo for long time?

 

[desertfox384]

I had the same exact issue last summer for about 3 or 4 months before I figured out what was wrong.. It was just the semi precious (I use Inline) and a few times it happened on my high noble, NEVER on the NP. I tried tons of things, spent a lot of time on the phone with Ivoclar etc... Changed my air filters, went over casting techniques, crucibles even bought a new air compressor. In the end I found it was one of two things.. I changed to a high quality aluminum oxide and also lowered the pressure i was blasting the metal copings down to around 3.5 bars and made darn sure it was an even dull gray surfrace when I was done blasting. This did the trick and I havent seen any bubbling for a year now.

 

[edohwin]

Its how its been sand blasted ,particles are staying on the surface or burnishing the surface. If you notice your np is fine look at your grit size and who is doing it . My feeling is they are blasting at 90 deg to the surface and not along the surface . Also the semi precious is a different heat conductor to np so if your using hot pegs under the copings you can be boiling the opaque liquid and causing voids between the metal and the opaque. Ive had techs tell me before that they are doing nothing different before, but when you go through the whole process yourself and nothing goes wrong you know its them and not the material which is what they want to blame ......I tell them they are sounding like a dentist then they listen.

I can potentially see how it may be a sandblasting issue because our sandblasters are quite old and they are set as 60 psi because lower doesn't seem to do much. Also I have no idea about sandblasting angle, can u describe it a bit better so I understand this concept? Am I aiming perpendicular or...?

Also if not metal pegs what should I use? Honeycomb only?

 

[edohwin]

Have you been using this alloy and porc/opaque combo for long time?

At least 1 year but like I said the bubbles are inconsistent. One thing I did notice is that a whole ring seemed to get contaminated while another ring of copings was safe. The contaminated ring was one where I reused a button that had been recycled 3 times already (and yes I add at least % 50 new metal)

 

[edohwin]

I had the same exact issue last summer for about 3 or 4 months before I figured out what was wrong.. It was just the semi precious (I use Inline) and a few times it happened on my high noble, NEVER on the NP. I tried tons of things, spent a lot of time on the phone with Ivoclar etc... Changed my air filters, went over casting techniques, crucibles even bought a new air compressor. In the end I found it was one of two things.. I changed to a high quality aluminum oxide and also lowered the pressure i was blasting the metal copings down to around 3.5 bars and made darn sure it was an even dull gray surfrace when I was done blasting. This did the trick and I havent seen any bubbling for a year now.

Question: what's ur procedure of treating the metal? Do u sandblast before degas and after degas? Do u use distilled water to rinse or do u just steam/air dry?

 

[charles hallam cdt]

It sounds to me as if somehow the contam is being introduced after blasting. B sure after degassing there is uniform oxide layer no lighter areas. From here work ur steps backwards to trouble shoot problem.u can try all suggestions which are all appreciated. But everyone's situation is different

 

[Mohammad Khair]

the last thing the lab may need is a sensitive material, its cost is extraordinary high even if it is of a cheap price, it might cost you your professional reputation which is very precious.
successful lab will find a practical material or free-size material that fit every single situation and consume the least amount of time, effort, and special treatments.

 

[edohwin]

some more pictures.. looks like the porcelain is tearing away from the metal.

 

[desertfox384]

Question: what's ur procedure of treating the metal? Do u sandblast before degas and after degas? Do u use distilled water to rinse or do u just steam/air dry?

For angle, (and this goes for any metal) try not to blast at a 90 degree angle, do more of a 45 degree especially at the margins. (I use callisto 75 from ivoclar) I finish my metal with white stones (shofu) evenly and no unfinished metal is visible.. then I blast at 3.5 bars well.. I make sure my tank is at least half full since it will not blast all that well if its low. Then i just steam with distilled water and place the copings on a tissue, walk over to the oven and place on metal pegs and degas.. then wash opaquer with a brush.

I realize to many here this seems like a metal contamination problem, and maybe it is.. but for me it was not at all. I didn't have bubbles quite that big like the last picture, but I did have smaller ones, sometimes there were tons of them.. they would show up on the final opaque bake usually and were very sporadic.. If I had 10 copings of the same metal maybe 4 of them would bubble....then the next batch wouldn't bubble at all.. It never made much sense and drove me insane trying to find the root of it all. You can check for even colors after degas but mine never once showed anything abnormal after degas.

At this point edohwin what you need to do is try anything that might help. Sounds like you have done just about everything you can - I would look to casting techniques and blasting/cleaning techniques. A miscalibrated torch can cause it. Maybe just ditch the metal and try a different kind if you can't figure this out.

 

[desertfox384]

Also, another thing to consider is decontaminate your ovens. Vision usa makes a kit http://www.visionusa.biz/product.php-p_id=80.htm

I use this every few months. My porcelain starts turning funky colors if I don't. Maybe it's what caused my bubbles to disappear, I'm not sure.

 

[Mohammad Khair]

the best way is just to throw away the sensitive material right out from the window, and stop being a babysitter for it, and use better materials that can stand all situations while trying to focus on our real job, let the manufacture take care of its materials research.
just don't bother your self for nothing.

 

[2thm8kr]

I would look to casting techniques and blasting/cleaning techniques. A miscalibrated torch can cause it. Maybe just ditch the metal and try a different kind if you can't figure this out.

LIKE

 

[Mohammad Khair]

always buy the horse that everybody can ride, leave the wild horses for cowboys.
beeee productive ya man.

 

[edohwin]

Good news for today - i got a new sandblasters renfert and used their sample beads as well. No bubbles whatsoever. I also tried re trimming and re doing the opaque on one's that showed bubbles from the day before and those came out good as well.

Mohammad I think the better oven has helped some of the problem. And I do think the metal I'm currently using is more sensitive then another semi we use as well. I'm gonna keep tracking it and figuring out what the main culprit was. I think it was a combination of a few things and all the little fixes are helping.

 

[Mohammad Khair]

Good news for today - i got a new sandblasters renfert and used their sample beads as well. No bubbles whatsoever. I also tried re trimming and re doing the opaque on one's that showed bubbles from the day before and those came out good as well.

Mohammad I think the better oven has helped some of the problem. And I do think the metal I'm currently using is more sensitive then another semi we use as well. I'm gonna keep tracking it and figuring out what the main culprit was. I think it was a combination of a few things and all the little fixes are helping.

best wishes

 

[desertfox384]

When I had bubbles I would blast of the opaque off and redo.. they always came out perfectly fine and bubble free after a second round of blasting and opaque, and I attribute that to it not being blasted well enough the first time. This may prove that its not a problem in the metal necessarily.