Jump to content


Photo

Hardened Zinc


  • Please log in to reply
16 replies to this topic

#1 Karen B

Karen B

    Potter 1981-present

  • Members
  • PipPipPip
  • 189 posts
  • LocationMassachusetts

Posted 24 October 2013 - 06:59 AM

My 50lbs bag of Zinc Oxide which is about 3/4s full has become hardened. I tried using some in a small glaze mixture by putting it in the blender but it did not work. Is there any way to salvage it?



#2 Marcia Selsor

Marcia Selsor

    Professor Emerita, Montana State University-Billings

  • Members
  • PipPipPip
  • 4,135 posts
  • Locationwhere Texas, Matamoros, Rio Grande and Gulf of Mexico come together.

Posted 24 October 2013 - 07:21 AM

put some in a bowl and dry it out in the kiln. fire it up to about 6-700 degrees.
It should breakdown easily after that.If not, take it to 1000 F. You could put some in a bisques bowl and fire it in a bisque and see what happens. That would be a truer calcination.test a small quantity first. I have done this for recipes that call for calcined chemicals. I use them as additions for things like slip going on dry pots. They shrink less.

Marcia

#3 Wyndham

Wyndham

    Advanced Member

  • Members
  • PipPipPip
  • 444 posts
  • LocationSeagrove NC

Posted 24 October 2013 - 11:02 AM

I think 1200 f is about as high as you should go. Zinc starts to vaporize at cone 06. Wiki says:

 

ZnO decomposes into zinc vapor and oxygen at around 1975 °C with a standard oxygen pressure. Heating with carbon converts the oxide into zinc vapor at a much lower temperature (around 950°C).[11]

ZnO + C → Zn(vap) + CO     Wyndham

#4 perkolator

perkolator

    Advanced Member

  • Members
  • PipPipPip
  • 340 posts
  • LocationCalifornia

Posted 24 October 2013 - 11:09 AM

mortar and pestle?  i would also try calcining it like suggested.



#5 Karen B

Karen B

    Potter 1981-present

  • Members
  • PipPipPip
  • 189 posts
  • LocationMassachusetts

Posted 24 October 2013 - 12:48 PM

Thank you so much! I am happy if I don't have to add the labor of mortar and pestle though.  :)



#6 Marcia Selsor

Marcia Selsor

    Professor Emerita, Montana State University-Billings

  • Members
  • PipPipPip
  • 4,135 posts
  • Locationwhere Texas, Matamoros, Rio Grande and Gulf of Mexico come together.

Posted 24 October 2013 - 01:11 PM

Thanks Wyndham. I wasn't sure of the higher temp. for vaporizing zinc. Drying it out in a kiln should dehydrate it. So try it at 6-700 F first and see if it breaks up.Or try 1000 F.
I do this with Calcium and Kaolin to make them calcined when the recipe calls for it or if I am experimenting with underglazes on dry greenware.

Marcia

#7 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 1,166 posts

Posted 24 October 2013 - 04:29 PM

 i have been known to put it in  a strong back and drive over it a few times in my small truck then sieve it/ mortar it as required.



#8 Wyndham

Wyndham

    Advanced Member

  • Members
  • PipPipPip
  • 444 posts
  • LocationSeagrove NC

Posted 25 October 2013 - 09:24 AM

If possible try to buy calcined zinc, it plays nicer with glazes than reg zinc. I think the 1000-1200 deg temp range drives off chemical water from the zinc, much like drying out a greenware pot where there's physical water and above 1000 deg f driving off chemical water but before sintering and fusing begins.

Wyndham



#9 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 1,166 posts

Posted 25 October 2013 - 06:45 PM

Ok As an isolated potter, self taught, reading many boks and articles, and watching carefully what happens!, what is the process of replacing Zinc Oxide with calcined ZincOxide in a glaze formula?

I'm not confident in replacing chemicals in my glazes as I have not had this education. I fire to C03 and also to C5/6



#10 Mark C.

Mark C.

    Advanced Member

  • Members
  • PipPipPip
  • 3,124 posts
  • LocationNear Arcata Ca-redwood rain forest

Posted 25 October 2013 - 08:58 PM

Zinc Ox always attracks water and clumps if left exposed in a paper sack or even a plastic bag over time.

You can store it in  mosture proof container

I keep mine up high in warm shop to keep it drier

I always mix the zinc portion of my glaze recipe in my blender with a little water and add it to the mix-warm water will help some.

Mark

 

For Babs (what is the process of replacing Zinc Oxide with calcined ZincOxide in a glaze formula?)

Say you need 50 grams of zinc oxide in recipe and you use calcined zinc Oxide instead-you would still add 50 grams.

Its just the same  about the without the water and its already shrunk.


Mark Cortright
www.liscomhillpottery.com

#11 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 1,166 posts

Posted 26 October 2013 - 02:07 AM

so there is no great weight loss associated with the removal of water? 

Does that apply to all calcined chemicals? I use calcined manganese dioxide sometimes and have some non calcined, ok to substitute?? Humidity would affect the water or is it a chemically bound water we are talking about here?

Try it I suppose!



#12 Marcia Selsor

Marcia Selsor

    Professor Emerita, Montana State University-Billings

  • Members
  • PipPipPip
  • 4,135 posts
  • Locationwhere Texas, Matamoros, Rio Grande and Gulf of Mexico come together.

Posted 26 October 2013 - 07:48 AM

Try it. It should dissolve better.
Marcia

#13 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 1,166 posts

Posted 26 October 2013 - 07:10 PM

Thanks every one. Did mean manganese carbonate not dioxide.



#14 Karen B

Karen B

    Potter 1981-present

  • Members
  • PipPipPip
  • 189 posts
  • LocationMassachusetts

Posted 25 November 2013 - 06:51 PM

As a follow-up to the problem with my hardened zinc:

I put about 6 very lumpy cups of the zinc oxide in a heavy previously fired pot .

 

 I heated it to 700 degrees and held for 20 mins. After cooling enough to open, I found that the lumps broke up, but was not fine enough to mix in a glaze. It would never pass through the 800 mesh sieve.

 

I tried sifting out the finest particles, but realized that I would never get the 2000 or so grams I would need.

 

I commandeered an old coffee grinder from the kitchen and found that it did the job. It quickly made the zinc into a fine powder.

 

I have glazed and fired with that zinc and glazes all look great. 



#15 Mark C.

Mark C.

    Advanced Member

  • Members
  • PipPipPip
  • 3,124 posts
  • LocationNear Arcata Ca-redwood rain forest

Posted 25 November 2013 - 08:39 PM

Why are using a 800 mesh screen?not much of anything will pass through that

I hope you meant an 80 mesh

Mark


Mark Cortright
www.liscomhillpottery.com

#16 Karen B

Karen B

    Potter 1981-present

  • Members
  • PipPipPip
  • 189 posts
  • LocationMassachusetts

Posted 25 November 2013 - 10:59 PM

Yes, Mark, I did mistype "80" mesh.

Thanks Norm for the source of information.



#17 oldlady

oldlady

    single firing an electric kiln to cone 6

  • Members
  • PipPipPip
  • 1,068 posts
  • Locationharpers ferry west va and pinellas park fl

Posted 26 November 2013 - 02:47 PM

norm, i know you want to be exact so maybe you want to re-read your "3 square meters per gram" line.


"putting you down does not raise me up."




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users