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Lab talk, the good, the bad, and the ugly
All Porcelain-Press
Emax greyish stains after glaze firing
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<blockquote data-quote="Patrick Coon" data-source="post: 144539" data-attributes="member: 11366"><p>The grey is usually from the organics in the glaze paste not burning off completely before the vacuum starts.</p><p>I would recommend not using the Vita firing paste for two reasons: </p><p>1. Additional organic load in the oven that will have difficulty burning off.</p><p>2. It contains a spun alumina fiber that will stick to the inside of the crown during firing and the only way to remove it is to sandblast with ALOX, which is a definite NO-NO with e.max after the restoration is final glazed. This will reduce the fracture toughness of your restoration by about 50% and also when you etch the restoration you do not get a good etch pattern for bonding/cementation.</p><p>If you must use a putty I would use one that does not contain the spun alumina (such as Object Fix),and only enough to secure the restoration on the pin. Just like Brylcreme – A little dab ’l do ya. That way during firing it will not add an extra organic load to the furnace and after firing it will wash out clean with a toothbrush and running water or a steam cleaner, no blasting required.</p><p> </p><p>Also, don’t overload your oven with restorations, I usually try to stay to 6 or fewer, and if it is a larger bridge lower your rate of rise to allow those organics in the fluids a little longer to burn off. Your vacuum should also start about 50C/120F after your furnace starts to heat up, this will allow the organics to volatize before the air is pulled out of the chamber. After the chamber pulls vacuum, they can no longer burn out and are trapped in the ceramic and turn it grey or black.</p></blockquote><p></p>
[QUOTE="Patrick Coon, post: 144539, member: 11366"] The grey is usually from the organics in the glaze paste not burning off completely before the vacuum starts. I would recommend not using the Vita firing paste for two reasons: 1. Additional organic load in the oven that will have difficulty burning off. 2. It contains a spun alumina fiber that will stick to the inside of the crown during firing and the only way to remove it is to sandblast with ALOX, which is a definite NO-NO with e.max after the restoration is final glazed. This will reduce the fracture toughness of your restoration by about 50% and also when you etch the restoration you do not get a good etch pattern for bonding/cementation. If you must use a putty I would use one that does not contain the spun alumina (such as Object Fix),and only enough to secure the restoration on the pin. Just like Brylcreme – A little dab ’l do ya. That way during firing it will not add an extra organic load to the furnace and after firing it will wash out clean with a toothbrush and running water or a steam cleaner, no blasting required. Also, don’t overload your oven with restorations, I usually try to stay to 6 or fewer, and if it is a larger bridge lower your rate of rise to allow those organics in the fluids a little longer to burn off. Your vacuum should also start about 50C/120F after your furnace starts to heat up, this will allow the organics to volatize before the air is pulled out of the chamber. After the chamber pulls vacuum, they can no longer burn out and are trapped in the ceramic and turn it grey or black. [/QUOTE]
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Lab talk, the good, the bad, and the ugly
All Porcelain-Press
Emax greyish stains after glaze firing
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