Eric Suchman on tue 28 jun 05
Hey all is this recipe for Mackersie copper a stable / food safe glaze?
Strontium Carb 15
Kona Feldspar 60
Dolomite 20
Bentonite 1-2
copper carbonate 2.5
(I realize it doesn't add up to 100 but this is from Lana Wilson's book
and I've copied it as is)
Thanks in advance,
Eeric on Oceanside
John Hesselberth on wed 29 jun 05
On Jun 28, 2005, at 8:57 PM, Eric Suchman wrote:
> Hey all is this recipe for Mackersie copper a stable / food safe glaze?
>
Hi Eric,
No, this will not be a very stable glaze. By my calculations the silica
level is only 1.55 vs. what I like to see of a minimum of 2.5
(preferably 3 or above) for a stable glaze. It is what I call an
unmelted matte, i.e. it is not a very high quality glass. I would guess
a slice of lemon would pull the color right out of the glaze.
Regards,
John
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
Ron Roy on fri 1 jul 05
Hi Eric,
As John says - not enough silica - so if you use it as a liner glaze it
will change the taste of some foods.
Think of it as an unstable glaze which will craze for sure - the craze
lines give any acidic food a greater area to work on - so even more
leaching will take place.
Many glazes with low silica craze because silica in glazes is an anti craze.
RR
>Hey all is this recipe for Mackersie copper a stable / food safe glaze?
> Strontium Carb 15
> Kona Feldspar 60
> Dolomite 20
> Bentonite 1-2
>
> copper carbonate 2.5
>
> (I realize it doesn't add up to 100 but this is from Lana Wilson's book
>and I've copied it as is)
>
>Thanks in advance,
> Eeric on Oceanside
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Jane Murray-Smith on fri 1 jul 05
Hi Eric,
I use mackersie copper on the outside of mugs and bowls...it is a beautiful
dry matte and doesn't craze. It needs to be on the right body. It looks
awful on Plainsman F97 or 340, but beautiful on M370 or Laguna Bmix.
The mystery of this glaze for me is that sometimes, for no easily analysed
reason, it will make little craters around the upper side of the join on the
base of a mug handle ...it also, when the batch was new, it would go dark
turquoise and glassy with little crystals where thick...an effect I have
sadly not been able to duplicate...thicker now results in more of those
craters..(unless it is that lovely pool right where it has glued itself to
the kiln shelf.....the humour of the kiln gods can be sooo sadistic!))
Put it on super thin or you'll be stuck to the shelf.
For a look at mugs with this glaze on the bottom of mugs, go to the
stoneware gallery on my website and they are at the bottom left corner.
www.dragonflypottery.ca
Jane
----- Original Message -----
From: "Ron Roy"
To:
Sent: Thursday, June 30, 2005 11:45 PM
Subject: Re: mackersie copper...stable?
> Hi Eric,
>
> As John says - not enough silica - so if you use it as a liner glaze it
> will change the taste of some foods.
>
> Think of it as an unstable glaze which will craze for sure - the craze
> lines give any acidic food a greater area to work on - so even more
> leaching will take place.
>
> Many glazes with low silica craze because silica in glazes is an anti
> craze.
>
> RR
>
>>Hey all is this recipe for Mackersie copper a stable / food safe glaze?
>> Strontium Carb 15
>> Kona Feldspar 60
>> Dolomite 20
>> Bentonite 1-2
>>
>> copper carbonate 2.5
>>
>> (I realize it doesn't add up to 100 but this is from Lana Wilson's book
>>and I've copied it as is)
>>
>>Thanks in advance,
>> Eeric on Oceanside
>
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
> Phone: 613-475-9544
> Fax: 613-475-3513
>
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