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#41 JBaymore

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Posted 11 May 2017 - 12:52 PM

I'm pretty sure more copper leaches from the water pipes in my house than will leach out of most cups in ordinary use.   There are certainly exceptions, and obvious situations where one should be aware, though.   Dump enough copper in a glaze that does not get fired to maturity, and you end up with real potential problems, that one needs to inform end users about.  product liability is a thing we need to pay attention to, in some locales and countries more than others.  Europeans have pretty strict labeling requirements regarding items that are not compliant with basic food safety rules.

 

Yup....... people seem to forget a LOT of houses have ...... COPPER pipes.  4% of copper oxide in a glaze batch that weighs 50 grams is on the inside of a mug....... that the water for the coffee or tea just came thru 100 pounds of copper pipes where maybe it sat since yesterday.

 

Any copper-bearing glaze that has the little black surface devitrification areas ("crystals") floating on the surface is absolutely not suited for food contact usage.  Copper compounds not well bound into glassy matrix and right on the surface.  Those glazes are beautiful.... and way off the mark on general "food safety" aspects.  Unfortunately, see them all the time on functional food pots.  Are they "death incarnate?  No.  But not good.  Back to the "good education" business. ;)

 

Anyone reading this thread that needs info on copper...... see the link Min posted above... I quote that one all the time.  As I've posted here many times...... Carty is " THE source" for good accurate glaze and toxicology info.

 

best,

 

....................john


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#42 oldlady

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Posted 11 May 2017 - 01:23 PM

john, your post above, #41 came up only 7 minutes after i asked a question that you would be the perfect expert to answer.  and your post is at the top of a page so mine is in no-man's land.  please read it and try to explain it to all of us non-chemists, self-taught and without a degree.

 

i did read Min's post.  it was written for chemists who understand all of the abbreviations.  i found myself constantly referring back to the table where the chemicals were listed to see what Na or Ca or whatever else was mentioned was.  by the time i re-read the original sentence i had to consider much more than the original sentence.

 

your reference to the problems with copper ( i use copper carbonate ) is not explained for those of us without your extensive background.  the Carty article says only that a glossy glaze (which mine is) fired above cone 1 (i fire to cone 6) should not cause any problems.  IF i read it correctly.

 

yes, i should go to college and get a masters degree but i will not.  must i be excluded from the basic knowledge you are discussing?


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#43 RonSa

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Posted 11 May 2017 - 02:58 PM

Then there are the foolish actions of the youth... I once made soup for lunch in the studio, and didn't have a bowl.  so I grabbed a copper bowl someone had made and used that.  Vomiting ensued in short order from the oxides and such that were still on the surface of the bowl after washing and had dissolved into my soup.  Lesson learned.  One must take precautions with things, and should follow best practices for safe glaze formulation, but paranoia is not necessary to the level that many people take it.

 

I guessing it may have been something else that might have made you sick. 

 

Copper bowls are a mainstay in whipping egg whites

The Science Behind Whipping Egg Whites in Copper Bowls

 

Copper bowls is also used for the preparation of caramelized sugar and honey in making candy.


Ron


#44 anchorman

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Posted 11 May 2017 - 04:49 PM

The copper bowls people use for egg whites and other culinary purposes tend to be clean of oxides.  Vomiting is one of the symptoms of consuming an acute dose of copper oxides - https://en.wikipedia...Copper_toxicity

I guessing it may have been something else that might have made you sick. 

 

Copper bowls are a mainstay in whipping egg whites

The Science Behind Whipping Egg Whites in Copper Bowls

 

Copper bowls is also used for the preparation of caramelized sugar and honey in making candy.

 



#45 anchorman

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Posted 11 May 2017 - 04:54 PM

the problem those of us who learn on our own is that none of these considerations are emphasized in the usual ways we learn.   maybe someone with the proper knowledge could write a simple explanation of why it is ok for mother earth to have deposits of chemicals and minerals that have been here for millenia but potters pouring some of those things onto the earth or into a river is wrong.

Depending on where these deposits are located they aren't necessarily leaching into the local water supply or various streams and rivers.  Often the nasty compounds are bound in ways that are less water soluble forms and as such are less harmful to various organisms in the environment, but after processing and refining by humans they become more concentrated, or are used in places where they have more potential to cause harm.  There are plenty of places where natural deposits of chemicals cause problems, such as areas that naturally have excess fluoride in the water.



#46 RonSa

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Posted 11 May 2017 - 06:15 PM

 

The copper bowls people use for egg whites and other culinary purposes tend to be clean of oxides.  Vomiting is one of the symptoms of consuming an acute dose of copper oxides - https://en.wikipedia...Copper_toxicity

I guessing it may have been something else that might have made you sick. 

 

Copper bowls are a mainstay in whipping egg whites

The Science Behind Whipping Egg Whites in Copper Bowls

 

Copper bowls is also used for the preparation of caramelized sugar and honey in making candy.

 

 

 

Yes, but you said...

 

  so I grabbed a copper bowl

 

...which is what I thought you were referring to.


Ron


#47 oldlady

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Posted 12 May 2017 - 07:09 AM

thank you, anchorman.  clear and concise.  by the way, my drains go to a septic system.


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#48 Joseph F

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Posted 15 May 2017 - 03:58 PM

On the bubble issue. I fired a grid tile for a clear that I am thinking about using. I have a bunch of the grid tiles with bubbles at different amounts. I made two of the grids for test purposes. I only fired one first in my normal schedule. I am going to add a hold at 2095F for an hour, based on that other schedule that I posted a few days ago. I want to compare the differences of that hold with my regular firing to see if it makes a difference like the schedule on digital fire said it would. 

 

I will post results next weekend when I fill my kiln with test and run it. I am curious if it really makes a difference.



#49 High Bridge Pottery

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Posted 15 May 2017 - 04:55 PM

Are you doing the hold on the way up? 


One physical test is worth a thousand expert opinions.

 

gallery_23281_871_611.png gallery_23281_871_239.png gallery_23281_871_701.jpg

 
 


#50 Joseph F

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Posted 15 May 2017 - 06:20 PM

Are you doing the hold on the way up? 

 

Yes. I will hold for one hour at 2095F on the way up. This is what insight said helps with the bubbles. We will see if it works or not. I have the extra grid, I might as well try it. It is for a clearish glaze. On my black clay, the clear is basically black, so that is what I want inside my my grey cups and mugs at the moment. So I want to fix the issue the best I can.. I will post the same tile without the hold and one with the hold and we can compare.



#51 Bryan Johnson

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Posted 15 May 2017 - 07:11 PM

What is the glaze like when you refire it?

 

Here are a couple of non-standard ideas that might take advantage of soluble borax.

 

Apply glaze to damp pot and let dry slowly, hopefully encouraging the borax to migrate to outer surface of glaze.

 

Apply a very thin layer of borax to an already fired pot, by heating the pot and then spraying a solution of borax on the surface.



#52 Joseph F

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Posted 19 May 2017 - 12:56 PM

There was no evidence that the hold at 2095F changed any of the tiles. I will look closer later but at first glance it did nothing. Just wanted to update. Still plenty of bubbles.

 

Edit: I went back and checked again with both grid tiles side by side. I noticed no difference in bubbles between the grids. If the hold at 2095F is supposed to reduce bubbles, it didn't do anything for me. 



#53 High Bridge Pottery

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Posted 19 May 2017 - 03:16 PM

Good to know, a hold on the way up or down seems to have no results at all.


One physical test is worth a thousand expert opinions.

 

gallery_23281_871_611.png gallery_23281_871_239.png gallery_23281_871_701.jpg

 
 






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