Charnley McCrorey on mon 28 jul 03
Hi,
I would dearly love it if someone on the list could help me figure out what
went wrong on something. First, I am a self taught sculptor and I have some
incredible gaps in my knowledge base. I also do some hand built or cast
functional stone ware. I make my own molds, I mix my own slips generally so there
are a lot of variables.
About 14 weeks ago I acquired and made some new molds. I decided to treat
myself and bought, for the first time ever, commercially mixed Laguna Stoneware
slip. I cast a number of pieces in both my own molds and the commercial
molds. All in all there were about 15 pieces cast with the 4 gallons of Laguna I
bought.
The stuff poured and cleaned wonderfully, I had a little trouble with some
rims cracking which I had not encountered before, but the bisque fires went
well. I bisqued to cone 06, the firing was a mix of Laguna pieces and pieces that
were cast from slip I made from my scrap and hand built stoneware pieces. I
allowed ample time to cool and set things aside to underglaze later.
My God daughter and her friend do my underglazing for me, I do the clear
glaze dipping.
The first problem is this, on every single Laguna piece we had a problem with
either the underglaze lifting or the glaze lifting and bubbling, both big
bubbles and pin hole ones.
The pieces that Bet underglazed while greenware held the underglaze fine.
But the clear overglaze on those pieces cracked and lifted (before firing).
The pieces that she underglazed on bisque it was the underglaze that lifted and
peeled. I was able to moisten it and lay it back down with a wet finger and
then brush the clear over it but I had to keep "smoothing it down".
This only happened on the insides of pieces, it happened on cups, Steins, Pie
plates and on these neat little poison jars.
The second problem was that the underglazes and the glaze on the Laguna
pieces took forever to dry to touch, I am not talking 15 minutes I am talking three
and 4 hours or more here.
What I need to understand is what happened and why it happened.
Can anyone enlighten me as to why it was only the Laguna pieces that did
this? has anyone else had this problem?
The bisque was wetted down before applying the underglaze. The witness cones
in the bisque firing were dead on the 06 firing. This didn't happen to one
single one of the pieces cast, or handbuilt out of my horrible junk clay slip I
make.
Thanks for any input,
Charnley McCrorey
Laughing Lion Productions
"Making silly little dragons to make people smile".
John Rodgers on mon 28 jul 03
Charnley,
I had a shop in Alaska for many years, and we used commercial slip that
came dry in 50 lb bags. We mixed it up ourselfs adding barium and
silicate to deal with the sulfates and adjust flow rates and
flocculation issues. Over time it was our experience that virtually ALL
commercial slips of that nature will periaodically cause problems due to
changes made in the ingredients in the dry mix. It happened to us
repeatedly over the years. It was a PITA and every time caused a great
"Wailing and Gnashing of Teeth" because we would have to go through a
period of adjusting glazes and underglazes to get everything working
together again. Spent a lot of extra time fussing with it. At that time
I didn't know how to mix slip and glazes from raw materials but did
learn later. And from what I learned, I wouldn't want to do it any other
way. Once you have a method that works for you, and know your
ingredients, changes in any big way can cause you a lot of grief. So the
trick is to test, test, test.
I find it ironic that you wanted to use a commercially prepared slip -
to give yourself a treat, and I wanted to give myself a treat by
learning how to make it for myself from scratch.
I guess my whole thing now is control over every aspect of my work, and
knowing how to mix my own glazes and clays, and make necessary
adjustments, is central to my success.
Not a solution for your immediate problem, but something to think about.
Good luck,
Regards,
John Rodgers
Birmingham, AL
Charnley McCrorey wrote:
>Hi,
>
>I would dearly love it if someone on the list could help me figure out what
>went wrong on something. First, I am a self taught sculptor and I have some
>incredible gaps in my knowledge base. I also do some hand built or cast
>functional stone ware. I make my own molds, I mix my own slips generally so there
>are a lot of variables.
>
>About 14 weeks ago I acquired and made some new molds. I decided to treat
>myself and bought, for the first time ever, commercially mixed Laguna Stoneware
>slip. I cast a number of pieces in both my own molds and the commercial
>molds. All in all there were about 15 pieces cast with the 4 gallons of Laguna I
>bought.
>
>The stuff poured and cleaned wonderfully, I had a little trouble with some
>rims cracking which I had not encountered before, but the bisque fires went
>well. I bisqued to cone 06, the firing was a mix of Laguna pieces and pieces that
>were cast from slip I made from my scrap and hand built stoneware pieces. I
>allowed ample time to cool and set things aside to underglaze later.
>
>My God daughter and her friend do my underglazing for me, I do the clear
>glaze dipping.
>
>The first problem is this, on every single Laguna piece we had a problem with
>either the underglaze lifting or the glaze lifting and bubbling, both big
>bubbles and pin hole ones.
>
>The pieces that Bet underglazed while greenware held the underglaze fine.
>But the clear overglaze on those pieces cracked and lifted (before firing).
>The pieces that she underglazed on bisque it was the underglaze that lifted and
>peeled. I was able to moisten it and lay it back down with a wet finger and
>then brush the clear over it but I had to keep "smoothing it down".
>
>This only happened on the insides of pieces, it happened on cups, Steins, Pie
>plates and on these neat little poison jars.
>
>The second problem was that the underglazes and the glaze on the Laguna
>pieces took forever to dry to touch, I am not talking 15 minutes I am talking three
>and 4 hours or more here.
>
>
>What I need to understand is what happened and why it happened.
>
>Can anyone enlighten me as to why it was only the Laguna pieces that did
>this? has anyone else had this problem?
>
>The bisque was wetted down before applying the underglaze. The witness cones
>in the bisque firing were dead on the 06 firing. This didn't happen to one
>single one of the pieces cast, or handbuilt out of my horrible junk clay slip I
>make.
>
>
>Thanks for any input,
>
>Charnley McCrorey
>Laughing Lion Productions
>"Making silly little dragons to make people smile".
>
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>
>
>
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