Opaque bubbling with porcelain shoulder problem...

[BruceQuality]

Hello!

We are experiencing a problem with our Finesse paste opaques (just a few) bubbling when a porcelain shoulder is being added to the opaqued coping on EDIT: Silhouette Line 250 SL, w/ almost 75% Palladium, no silver. Has anybody else experienced this? Did you find a remedy if so?

The shades we are experiencing this with are: A0, A3, A4, B1, C1 and D4.

Our opaguing technician worked in another lab a few years ago and experienced the same difficulty with their silver palladium, a different metal than ours. So we now know that this is not an isolated issue and it began before she arrived, so it is not isolated to any individual in the lab either.

Thanks for any/all input!

 

[DMC]

I'd say any bubbling is contamination. Any rubber or silicone introduced into the metal by accident? Maybe Polishing compounds, or residue from a soft tissue piece? Was metal sent for tryin?

Can you repeat your problem with any coping using the same material (although your shades listed are the most common shades we get pretty much)?

Then throw that tube out I guess? (I don't use that porc.)

Silver has been known to discolor, but I don't know about bubbles?

??

 

[zena]

We do two layers of opaque. During the first layer will make sure to have an 80 % coverage, I place my honey comb tray on a coffee warmer plate which I have plugged in on my bench for this purpose only "I swear" to let my copings dry, before I put it in the furnace. I make sure I'm not putting it directly in hot furnace in which someone just came out of, because this burst of hot heat causes cracking in the opaque. Always make sure your opaque is dry not wet or to thick when it's going in the furnace. I hold the crown with the hemostats as I opaque, and once my first layer is on I tap on the hemostats slightly to vibrate the wet opaque and then set in on the honey comb tray which is already on my coffee warmer and let it dry takes a couple minutes. For my second layer I do the same. If I were to see cracks I would not opaque over that cause that would cause a weak base for the porcelain to sit on. I would sandblast off the lifted opaque areas and re opaque. Also make sure you start off with clean metal and avoid touching with your hands because the oils on our fingers could contaminate the metal.

 

[DMC]

i think this guy is having bubbles, not cracks.

I agree with your method for drying paste opaque to avoid cracks from rapid heating.

You could lower your low temp on opaque cycle and achive the exact same effect.

With oven open and a low temp of maybe only 250c would have the platform close to coffee temps.

Then just use the recommended drying time (usually 6min or so) for program and hit start and walk away. That's how I'd do it??

I've never had oil or food products from my hands give any problem at all.
The compounds that give me trouble are silicone from polishers and soft tissue, and from impressions taken with the framework in them. Silicone has a very high melting temp and does not play well with porc.

Any rubber material or petrol product is bad of course. Synthetic carpet fibers are mostly petrol, wool will burn out fine. Rouge and other metal polishers will cause bubbling.

I have not heard about silver alloys causing bubbles, but I surely don't know everything. Maybe it does?? I've never used a silver-alloy with Porc. I use Silver-free. It does cost more I guess? Like $1.

 

[sixonice]

Bubbles in the opaque (or that go down to the opaque) indicates a problem with the alloy itself. It is one of two things: improper metal finishing (be certain to follow the manufacturers recommendations on finishing with burs and/or non-contaminating aluminous oxide stones, blasting pressure and proper oxidation sequences!) OR you have castings that have contaminated alloy. When I say contaminated, I mean a button that was overheated or burned up & mixed with fresh alloy. I would start with new fresh alloy & review the metal finishing, and I think you will be good to go. It has nothing to do with the fact your using a semi-precious with silver.

 

[TheLabGuy]

It has nothing to do with the fact your using a semi-precious with silver.

Actually it could if the silver is creating an oxide layer that isn't being removed before opaque. I'm not a metallurgist but silver and cobalt both cause distinct oxide layers after first firing. However, I'm with you, it's probably mixing good/bad alloy, or finishing with bad stones....I will say though, when I used Finesse (Low Fusing),we always had to use silver free alloys. Might be something to look into.

 

[BruceQuality]

Thanks for the replies so far!

As an update, I had incorrectly identified our metal we are having problems with. The metal is actually silver free, it is Silhouette Line 250 SL with almost 75% Palladium, sorry for the misinformation.

Also, this only happens during the shoulder bake, not when the opaque is applied the first time.

Thanks!

 

[magushnik]

out of curiosity when ure sandblasting ure using non recyclable sand right?

 

[BruceQuality]

Mag,

Correct! We are using 50 micron aluminum oxide.

 

[zena]

BruceQuality you said..."this only happens during the shoulder bake, not when the opaque is applied the first time." this is weird, check you firing temps, do you calibrate your furnaces?

 

[DMC]

Someone is rubber-wheeling the metal for the porc cut-back or using a weird tool and not cleaning.

That's my guess....contamination. What's the prize for winning?


When you say shoulder bake, I'm guessing you mean a PBJ?
Porc. Butt Joint.


Allah Peanut Butter Sandwiches!

 

[Al.]

It usually takes a few bakes for the bubbles to start showing up. Your shoulder bake would be your 3rd and 4th bake. If no shoulder then they come out in your 2nd porc bake. At least that is how it has always worked for me. I usually scrap the button. And even the crucible if it is contaminated.

 

[BruceQuality]

Another shade did it today...

We had another shade bubble on us today A1!

So now our list is growing to: A0, A1, A3, A4, B1, C1 and D4.

It has also happened everywhere from the first opaque bake through the porcelain firing. This includes porcelain shoulders (butt joint) and non-porcelain shoulders. It does most often occur during the 3rd or 4th bakes.

Our metal department insists that it isn't anything they are doing...

Our opaquer has tried different things including ultrasonicing the copings...

I also apologize for getting the story in bits and pieces...As my name suggests, I'm Quality and I'm trying to find out what is happening from each department and getting the whole story together.

We are at a loss for ideas...

Thanks for any/all assistance!

 

[yooper886]

I have not done any c&b in some time but when this stuff would start to happen to us we would scrap all our buttons and start out with nothing but new alloy, do the same thing with the crucibles and also our finishing burs. If that is not an option can you at least maybe track it to a tech that is doing the metal finishing or is it happening with multiple techs?

 

[BruceQuality]

Yooper,

You have hit upon the direction I'm leaning...We want to make changes one at a time so we can identify the exact problem. I'm starting to track which techs are doing what and see if that leads us anywhere.

Thanks!

 

[aidihra]

Check to see if the metal department is using the same burs to trim the precious and non-precious metals. Make sure when trimming the metal it's all in one direction so air pockets don't form.

 

[BruceQuality]

Experiments...

We are running tests on two pennyweight of SL in ingot form as they came from the refiner. This means no metal department work has been done on them to eliminate the possibility of contamination from there.

Also, we have found out that two of the ingredients of the paste opaque ATTRACT water...Since this problem seems to happen in the spring and fall of the year when it is the most humid here, we are thinking that the opaques are attracting moisture while sitting in the trays on the bench. To eliminate or confirm this, our opaquer will be using only a little opaque in the tray at a time and cleaning it out between batches and not letting it sit on the bench. We have also set up a humidity meter to see how much humidity is in the room.

Right now the humidity seems to make the most sense, but I'll keep you informed.

Thanks for any/all assistance!

 

[charles007]

Bruce,
Water on your brush or crown will create bubbling tearing with any brand of paste opaque....... The problem that I can't figure out is, you are only seening this problems with certain shades, if I understand what you said, doesn't make any sense...........unless bad porcelain.
If you are keeping paste in a storage tray, that shouldn't be a problem unless maybe its near a hot heat source... I would look more at the use of cleaning the opaque brush with water. Watch how your opaque person opaques when changing shades and cleaning the brush.... I just wipe the brush on tissue between different shades or clean with water then drop of opaque liquid on brush, then blot brush on tissue again.
Also check with Ceramco for bad batches of porcelain, since you are running out of places to look for problems.

Charles

 

[sixonice]

I am almost certain that using all FRESH, NEW ingots of alloys AND A NEW CRUCIBLE will solve your issues. Like I stated earlier, I believe you are rotating a contaminated button in your melts. Discard all your buttons and refine them. I do not think is has anything to do with your opaques, they are fine. NEW alloy & a NEW CRUCIBLE should solve your issues.

 

[charles007]

sixonice,
Contaminated button and crucible can create all kinds of gassing problems...... Please explain why all shades are not gassing, including non shoulder crowns, and expecially pontics where you would see the most gassing if there is some sort of contamination....