Bubbling in Vita VMK Master opaque! *PICTURES

[edohwin]

you can solve it also by changing your opaque to a less sensitive one.
for example ceramco2 opaque with crystals is a criminal opaque and can withstand mostly any small problem like that one.
a friend of mine have use it with vita for more than ten years with no problem at what so ever level.

I may need to try this ceramco2 opaque!! (it works with VITA VMK?) i'll look into it. Thanks.

from pics it looks like metal contamination. All new metal. ( i know one tech uses real cheap NP, discards every button after casting once) clean torch tips, use new crucibles. I always used stones, check with stone manufacturer to be sure binder in stone is OK with NP, on NP and then sandblast with aluminum oxide. then throw in distilled water for a few minutes then dry and heat treat. Please remember distilled water is only clean the first time, if you reuse it is no longer distilled h20. Good luck this kind of stuff is very frustrating.

Funny thing is, ALL our NP is fine. It's the semi precious that bubbles. I'll check on the stones if the new oven doesn't work

Thanks again guys.

 

[Mohammad Khair]

I may need to try this ceramco2 opaque!! (it works with VITA VMK?) i'll look into it. Thanks.




Funny thing is, ALL our NP is fine. It's the semi precious that bubbles. I'll check on the stones if the new oven doesn't work

Thanks again guys.

best wishes

 

[charles007]

I may need to try this ceramco2 opaque!! (it works with VITA VMK?) i'll look into it. Thanks.




Funny thing is, ALL our NP is fine. It's the semi precious that bubbles. I'll check on the stones if the new oven doesn't work

Thanks again guys.

Check your PM
Just sent you one..
Charles

 

[Mrs.galfriday]

You can't suck and blow at the same time.

Some can...er sorry. I couldn't resist that remark. * snark snark

 

[dmonwaxa]

Alloy contamination,,,,,PERIOD!!!

 

[edohwin]

Update today:

I decided to use all new metal (no buttons) and use a new furnace. Kept everything else the same. Seems to have done the trick so far.... Going to try reusing the button from today's castings and use the same oven monday and see if that changes anything.

 

[aqdental]

It's weird... some days it will be really bad like 10 or more copings are ruined and then another day maybe only 1 or 2 issues pop up then the following day none.

Maybe it is an inconsistent vacuum. I'll try opaquing with newer oven and better vacuum. Then see from there. Changing ovens seems like the easiest thing to do right now. Then I'll move onto the other things like burrs and casting technique etc.

Hi Edohwin, next time opaque copings from the same casting ( same ring) an see the result. If only some produce bubbles maybe its not casting the issue. Keep doing this to reduce variables.

 

[dmonwaxa]

Its not your oven, anytime you see opaque flaking off its because the bond is affected. How does this happen you ask? One way is there is a problem with the bond at the metal ceramic interface. On a molecular level the alloy create metallic oxides when subjected to a high enough temperature. This is called oxidation also known as degassing...a misnomer. When opaque is applied to the alloy and treated to a high enough temperature it releases metallic oxides also. The ceramic molecules of the opaque is released and is transferred across the oxide layers and forms a bond at the interface. Alloys that are habitually reused, melted at high temperatures without sufficient new alloy added, lead to bond failure because the metals that create the oxides become depleted. It not only affect the bond, but can cause CTE issues down the road. Usually after shipping and seating.

Also using the same crucible for different alloys is asking for trouble.

 

[Mohammad Khair]

Update today:

I decided to use all new metal (no buttons) and use a new furnace. Kept everything else the same. Seems to have done the trick so far.... Going to try reusing the button from today's castings and use the same oven monday and see if that changes anything.

thank you for the update
glad your problem have been solved
wish you all the best

 

[edohwin]

Its not your oven, anytime you see opaque flaking off its because the bond is affected. How does this happen you ask? One way is there is a problem with the bond at the metal ceramic interface. On a molecular level the alloy create metallic oxides when subjected to a high enough temperature. This is called oxidation also known as degassing...a misnomer. When opaque is applied to the alloy and treated to a high enough temperature it releases metallic oxides also. The ceramic molecules of the opaque is released and is transferred across the oxide layers and forms a bond at the interface. Alloys that are habitually reused, melted at high temperatures without sufficient new alloy added, lead to bond failure because the metals that create the oxides become depleted. It not only affect the bond, but can cause CTE issues down the road. Usually after shipping and seating.

Also using the same crucible for different alloys is asking for trouble.

I do reuse the bottons but try to add sufficient amounts of new metal in. I'll try to keep the ratio better tho. We have separate crucibles for each different metal.

thank you for the update
glad your problem have been solved
wish you all the best

One little issue tho. I took a coping from the other day that was definitely giving us bubbles (we tried opaquing 3 times). We did it with the same batch that was all perfect on friday and this one bubbled. I'm not 100% sure if the metal was contaminated to the point that no matter what furnace we used it would still bubble, but it did bubble.

So I'm going to keep searching, but new furnace seems to have helped. We shall see if the porcelain tears off the opaque which it has been known to do.

 

[Mohammad Khair]

I do reuse the bottons but try to add sufficient amounts of new metal in. I'll try to keep the ratio better tho. We have separate crucibles for each different metal.




One little issue tho. I took a coping from the other day that was definitely giving us bubbles (we tried opaquing 3 times). We did it with the same batch that was all perfect on friday and this one bubbled. I'm not 100% sure if the metal was contaminated to the point that no matter what furnace we used it would still bubble, but it did bubble.

So I'm going to keep searching, but new furnace seems to have helped. We shall see if the porcelain tears off the opaque which it has been known to do.

thanks again for update, a photo of that bubbled coping would be very helpfull

 

[PDC]

Paste opaque
Low temp is 500
We put the pegs on a hotplate to dry them before going into the oven

the contamination must be something that is inconsistent before it isn't always happening.. inconsistency is what is the most frustrating

You need to lower your entry temp to 400. Palladium alloy has a higher conductivity than NP. As a result the metal heats the opaque liquid too quickly causing the blisters. I use the same opaque on a palladium based alloy with an entry temp of 410 with no problems. You don't need to do the hot plate option...just lower your entry temp. Best of luck.


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[charles hallam cdt]

How old are your airlines and dryers

 

[charles hallam cdt]

Hope not repeatn myself but check line dryers and air lines make sure ur not blasting contamination on ur alloy. Otherwise trouble shoot from step one to final changing only one variable at a time. Good luck

 

[edohwin]

Ok so day 3. I reused the bottoms from the fresh metal i started with on day 1.

Got a few occurrences now of bubbles. Please have a look

http://postimg.org/gallery/7m1hnl6k/0e91435b/

keep in mind not all the batch of metal created bubbles so what could it be?

 

[Mohammad Khair]

what furnace ur using, how old is it , and what the vacuum read on it after 3 minutes of start of the vacuum, take a photo of its screen.

 

[edohwin]

I'm using a brand new vita oven recently purchased about 1 month ago .. New vacuum and everything
vacuum reading 100%

 

[Mohammad Khair]

u have basically two reasons for this
1- malfunction vacuum 80%
2- incompatibility between the metal alloy and the opaque 20%, you need to change one of them

 

[Mohammad Khair]

i told you how to make a practical check for vacuum, go back to post number 36

 

[grantoz]

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.