treating metal before opaque

Bobby Orr ceramics

Bobby Orr ceramics

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NEVER USE A GREEN STONE OF ANY KIND ON ANY ALLOY !!! most stones are created with plastic binders to hold the grits together. As the stone heats up , you're melting and smearing the plastic into your metal surface. You're screwed from that point on.

Use a diamond or carbide ..... or if you like a disc...... Talladium has an awesome disc called a WearEver disc. These discs are 100% aluminum oxide that is heat pressured when fabricated. No binders at all. They work awesome on any alloy surface.
 
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squarebiovest

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Oxidation depends on Chromium, Molybdenum, Beryllium and lastly Aluminium percentages.

Moly and Bery are used as grain refiners in alloys and also to provide strength. But at elevated temperatures Chromium reacts to oxygen forming chromic oxide on metal.

Aluminium in regard lowers the amount of chromic oxide formation. As the metal solidification occurs chrome also reacts with the binder composition of the investment. Thus giving a green color on contact layers of investment after castings. The cooling of investment if drastic the more the green color. Also the cooling is for providing better grain structure to the metal and hence addin to strength.

Answer to your question is: why consider only metal, consider your ceramic system also. Not all materials are compatible different alloys. There has to be a very thin layer of oxidation on metal surface to adhere and promote ceramic bonding. Metal to opaque to body.
 
cheadlemick

cheadlemick

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Not to mention Van Der Waals !
 
JohnWilson

JohnWilson

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In a Nickel Chrome alloy if there is at least 26% chromium it negates the toxcicity of the individual elements as in amalgam e.g. mercury and silver! However beryllium is a definite no no!

This is not what I was taught but none-the-less its good info for me to do some research. Since I do not use NP I don't really care, just looking out for my fellow techs. I guess maybe I have just been regurgitating what I have been taught so many moons ago that I really do not know. I will say this that there is a reason that the highest percentage of allergic reactions are based on nickel sensitivity. I know this is a fact :)
 
cheadlemick

cheadlemick

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Hi John,Nickel that is correctly alloyed isn't as great a problem and i would say that millions of crowns have been made in the last 40 years without too many problems.Cobalt and chromium on their own are toxic! As is palladium!
 
cheadlemick

cheadlemick

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In fact some of the early porcelains contained radioactive materials to give them a natural flouresence!
 
corona

corona

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.Cobalt and chromium on their own are toxic! from cheadlemick .

Cheadlemick ... the new stable priced alloys coming out that are co/chrominium like the noblenf from argen .. do you think that they are safe to use ??
 
Edy

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.Cobalt and chromium on their own are toxic! from cheadlemick .

Cheadlemick ... the new stable priced alloys coming out that are co/chrominium like the noblenf from argen .. do you think that they are safe to use ??

well now i dont know what to use then , 60% ni and 26 cr in my ugirex alloy is toxic , now u say the co/cr alloys are toxic too , then what option are left ? if all alloys are toxic then i should stck with my ugirex alloy no ? at least i know it because i work with it almost a year now
 
cheadlemick

cheadlemick

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It's all to do with the correct percentages of the materials.To be fair any material breathed in could be considered dangerous so always ensure plenty of care when processing metal!
.Cobalt and chromium on their own are toxic! from cheadlemick .

Cheadlemick ... the new stable priced alloys coming out that are co/chrominium like the noblenf from argen .. do you think that they are safe to use ??
 
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Alexsasax

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on vita is 1st firing is 960 with 80 rate , and 2nd 950 80 rate, noritake has 1000 , 65 rate1st and 2nd opaque , and what i heared that u can apply only one coat without a second opaque needed . . .

Sry for my bad english :) Your HT is too high. Bond at 980, Noritake ex3 opak at 970 and Vita 930 ( my opinion based on lot of work with both:)). And metal with 62% Ni is bad.. For u and for patient.
 

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