Welcome to The BRIDGE, the social and information hub of the dental lab industry. Connect with industry peers and vendors, ask questions, sign up for events, review products, read LMT articles and industry news and more!
December 16, 2012
Could you please let me know the alloy and the brand of this alloy? By the way when do you start to have this problem?
tell me what you do after metal work is finished dont listen to what kind of metal you are using or tip needs cleaning
I have had this also, please let us know what type of metal and if it is a press to metal porcelain. I am just curious if it is the same I have used that I have seen this with. I am not saying it matters I am just curious.
A possible contributing factor to bubbling is the firing temperature of your first opaque cycle relative to the oxidation cycle temperature. If you are oxidizing the alloy prior to opaquing, even if you then blast off the oxide layer before you apply opaque it is very important that your first opaque firing does not go to close to the oxidation temp. You want to stay at least 20 degrees Celsius below the oxidation temp. Your second opaque firing should be 10-20 degrees lower than your first opaque firing. Hope this helps.
I agree with Jeff. It's likely contamination of the metal from finishing stones. We had problems when a stone used for removing oxides from implant cases before polishing was then mistakenly used to finish copings. If any of the metal from the machined gold interface gets into the stone, it can no longer be used for finishing.
If you are using base metal alloys frequently, you may want to look at using some type of furnace purging material. It will help to remove many contaminants that attach themselves to the muffle and thermocouple. You would want to do this weekly if using predominantly base metal alloy.
It is always best to follow the manufacturers recommendation for surface treatment of the alloys, although, all of these recommendations are great.
It's most likely from contamination somewhere in the process of conditioning and opaquing, as I'm sure you realize. Here's what I do to avoid the same thing:
First, I use specific finishing/grinding tools for each metal and I don't cross contaminate. When using stones, I only use aluminum oxide.
Second, I fiinsh my metal in one direction, never crossing over perpendicular to previous grindings , or reversing direction. This can fold metal over and cause bubbling later on.
When I'm finished...(more)
May want to replace the Muffle even if you just had done this in the last few months. Also, we had this happen while we used rubber gloves while opaquing that were contaminated.