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    Porosity on semi precious

    Discussion in 'Metal' started by Dimis, Nov 17, 2016.

    1. Dimis
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      Dimis Member Full Member

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      Hi guys i m doing a semi presious alloy( for the first time)cerapall 6 and im using EX3 noritake . I did oxidation but on the first opague it was full of porosity can somebody give me any advice
       
    2. CatamountRob
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      CatamountRob Banned Member Full Member

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      Is it a high palladium alloy?
       
    3. RDA
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      RDA Active Member Full Member

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      With the Noritake EX3, go with a thin wash opaque for your first opaque firing. If you mixed the oily liquid that is on top of the opaque in the jar, this will cause the porosity to occur. That liquid is meant to keep the opaque from drying out in the jar only. Tilt the jar and take your opaque from the side. I fire EX3 on semi precious metal everyday for years, and it fires beautifully. Hope this helps.
       
    4. Dimis
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      Dimis Member Full Member

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      Yes its high in palladium


      Sent from my iPad using Tapatalk
       
    5. CatamountRob
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      CatamountRob Banned Member Full Member

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      I'm not familiar with Noritake porcelains, so it may be just as RDA is saying, an issue with the opaque application.
      If you're casting with a torch, be very careful with your torch settings, palladium has an affinity for oxygen and carbon and is easy to contaminate.
       
    6. SiKBOY

      SiKBOY Member Full Member

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      I use 80% palladium with noritake ex3. Go with what rda has suggested or a longer dry time.
       
    7. Car 54
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      Car 54 Well-Known Member Donator Full Member

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      Make sure you're using non contaminating i.e. red, pink discs/stones to finish your metal. Semi precious is softer and contaminated discs could cause bubbling or porosity.
       
    8. PDC

      PDC Active Member Full Member

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      Sounds like you might need to lower your entry temp and increase your dry time. Also, I usually do 2 oxidation cycles...blast off the first and then do another. I've noticed that the opaque looks smoother doing it this way.
       
      Last edited: Nov 17, 2016
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    9. Getoothachopper
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      Getoothachopper Well-Known Member Donator Full Member

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      I agree with Cat ....... The few times iv'e had the opaque blow off the metal it was because I was missing the reduction zone in the torch and contaminated the metal .:(
       
    10. doug
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      doug Well-Known Member Donator Full Member

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      What is your top temp during the first opaque firing? It may not be high enough
       
    11. Juko

      Juko Active Member Donator Full Member

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      Some alloys require the oxidation later to be removed prior to opaquing. Check the specs on that.
      Thin layer of opaque the first firing, don't let it pool.
      Noritake recommends drying on a hot plate for 5 to 8 minutes prior to firing. I don't do this for the first layer however I do for the second layer except I don't have a hot plate. I just close the furnace with a firing tray in there and then pull it out when I'm ready for it and let it set on there outsida the oven until it's almost dry then I stick it in the oven and let the oven close and do it's thing.
       
    12. Car 54
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      Car 54 Well-Known Member Donator Full Member

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      I've found that to be especially helpful for Noble metal. I don't really have any problems with HN, but if I have any issues, in my case more to do with bubbling (than porosity?) it will be with noble metal, and running 2 oxidation cycles, blasting off the first, takes care of it.
       
    13. rkm rdt
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      rkm rdt Well-Known Member Donator Full Member

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      mix your paste opaque really well and use a plastic or glass instrument to apply a thin layer of paste.
      Slow dry under your open muffle for 5 mins minimum.

      We never degass our alloys. Just metal finish and sandblast then opaque.
      One opaque layer of ex3 is all you need when you get the hang of applying an even coat.
       
    14. PDC

      PDC Active Member Full Member

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      I think the first oxidation cycle burns out any impurities in the metal which are then deposited on the surface. I know we all blast before oxidizing, but some of those impurities are just underneath the surface. Blasting that off after the first oxidation cycle and re-oxidizing helps to get rid of that thus producing less bubbling in the opaque.

      In regards to the high palladium alloys, I think they heat up faster than the higher gold containing alloys. It would seem logical since they are less dense and lighter in weight. That is why you need to lower the entry temp so you don't "boil out" the opaque liquid to quickly.
       
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    15. CatamountRob
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      CatamountRob Banned Member Full Member

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      Anytime I don't see a nice uniform oxidation layer on a high palladium alloy, I sandblast it and try again. In most cases the second time it will look nice and even as PDC is saying.
       
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    16. TheLabGuy

      TheLabGuy Just a Member Full Member

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      DO NOT STEAM YOUR COPINGS...this doesn't sound like your problem, but with all metals, especially with noble, you will contaminate your copings using a steamer after you sandblast them. The new steamers on the market have a teflon coating on the heating elements, that when heated contaminates the distilled water in the steamer. The teflon type coating is nice because it makes your steamer last for years, but its incredible what that steam does to your copings...makes bubble city!!! Use distilled water and ultrasonic cleaner for a few mins after sandblasting them.
       
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    17. Car 54
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      Car 54 Well-Known Member Donator Full Member

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      Interesting post, LabGuy, as I'd not thought of that one. Maybe all my teflon tape has lost its contaminating effect? So far it's just the noble metal that gives me grief once in awhile, due to overheating during casting, or the impurities that need to be burned out, then blasted as PDC mentioned. Maybe I've just been lucky, or should make that change?
       
      Last edited: Nov 18, 2016
    18. TheLabGuy

      TheLabGuy Just a Member Full Member

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      Try it and let us know...bet your bubbles dissappear :)
       
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    19. Car 54
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      Car 54 Well-Known Member Donator Full Member

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      What do you do to get rid of the etched surfaced from emax? I usually steam the white layer off, could that contaminate the etched surface? Does the ultrasonic do a good job in shaking off the etched white layer?

      Thanks :)
       
    20. rkm rdt
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      rkm rdt Well-Known Member Donator Full Member

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      take a big mother heatless stone , turn off your vac and crank up some "crazy train".

      You may not prevent contanination but the flying shards imbedded in the faces of your co workers is definitely worth the pink slip!
       

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