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Lab talk, the good, the bad, and the ugly
Porcelain
Cracked up!
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<blockquote data-quote="JonB" data-source="post: 45832" data-attributes="member: 3047"><p>No anti rotation grooves in any preps.</p><p></p><p>We follow the oxidation firing to the letter - as we have for the 20+ years we've used this alloy</p><p></p><p>I believe the opaque formula may have changed more so than the alloy - but either is possible.</p><p></p><p>UPS is handling the shipping and we're not having this happen on high noble or other doctors we ship to (unless they aren't telling me - and why would they not?)</p><p></p><p>--</p><p>I've tracked the lot numbers and not seen that that makes any difference, this has occurred over three separate lot numbers. I've replaced old crucibles with new ones. I've cast all fresh alloy and cast 40/60 mix old/new alloy - and no difference in frequency of the problem. We use Renfert Cobra 100 micron for divesting and 50 micron Cobra for pre-oxidation bake cleanup after finish. I've used A/O Rubi stones for years to finish and #1 & #2 burs inside for seating.</p><p>Possible contaminants from high speed NSK handpiece/air line seems unlikely as we'd see spots where oil or debris would show up in the oxidation. Same with anything coming out of the steamer. We have even ran batches of copings just in the ultrasonic instead of steam to see if any difference.</p><p></p><p>There is no one conclusive thing that jumps out. Seems like if i were finishing the margins too thin, it would be on the HN alloys as well - maybe more so since its a bit softer and more likely to deform.</p><p></p><p>In the past its been Ceramco paste opaque on 75+6 alloy with either Synspar porcelain or Noritake. We dropped the Synspar almost a year ago. Today will be the first day using the Noritake opaque on all cases.</p></blockquote><p></p>
[QUOTE="JonB, post: 45832, member: 3047"] No anti rotation grooves in any preps. We follow the oxidation firing to the letter - as we have for the 20+ years we've used this alloy I believe the opaque formula may have changed more so than the alloy - but either is possible. UPS is handling the shipping and we're not having this happen on high noble or other doctors we ship to (unless they aren't telling me - and why would they not?) -- I've tracked the lot numbers and not seen that that makes any difference, this has occurred over three separate lot numbers. I've replaced old crucibles with new ones. I've cast all fresh alloy and cast 40/60 mix old/new alloy - and no difference in frequency of the problem. We use Renfert Cobra 100 micron for divesting and 50 micron Cobra for pre-oxidation bake cleanup after finish. I've used A/O Rubi stones for years to finish and #1 & #2 burs inside for seating. Possible contaminants from high speed NSK handpiece/air line seems unlikely as we'd see spots where oil or debris would show up in the oxidation. Same with anything coming out of the steamer. We have even ran batches of copings just in the ultrasonic instead of steam to see if any difference. There is no one conclusive thing that jumps out. Seems like if i were finishing the margins too thin, it would be on the HN alloys as well - maybe more so since its a bit softer and more likely to deform. In the past its been Ceramco paste opaque on 75+6 alloy with either Synspar porcelain or Noritake. We dropped the Synspar almost a year ago. Today will be the first day using the Noritake opaque on all cases. [/QUOTE]
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Lab talk, the good, the bad, and the ugly
Porcelain
Cracked up!
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