Thursday, March 12, 2009

Cold potting.

Today I woke up to cold rainy weather and had to fight the urge to stay in bed a couple more hours. I made it up to the studio where it was also quite chilly. Today will be filled with mostly trimming and slipping so I think I can handle it.

The last couple weeks we have had unusually warm weather, 70's & 80's even hit 90 a couple days. Texas is generally warmer than everywhere else but we still should be in 50-low60's. Yesterday it dropped from 83 down to 41 in a matter of hours and started raining. Some of you may be thinking "40's aren't so bad, it's not even below freezing, what are you complaining about?" It's not the actual temp that bothers me so much as the drastic change which is commonplace here. It's fairly normal to shift 30-40 degrees in a day in the spring and fall, annoying. Anyways, moving on.

I've been steadily potting the last few...well yesterday actually. It's nice to get back into the clay. I was hoping to get a firing out before my show in Houston on Mar.27 but that is going to be a bit of a longshot. It takes about 200 pieces to fill the kiln and I have about half that ready to go(stacks of bisqueware in background). So I have to produce another 100 pieces give or take which can be done over the next couple days but getting them dried and bisqued in time is what makes it a longshot. I have enough pots to show with but it would be nice to draw from a larger pool of work, so I'm ok either way.

I fired a little test kiln yesterday with some ash glaze tests. I've used the same formula for my basic 442 green ash for a few years but the color is far different than what it used to be. I don't know if it's the ash changing or the other raw materials. So the first row here is the base with no colorants and then starting with .5% up to 2% RIO, the last tile is 3% red clay which strangely enough is lighter than the base with no iron. I've been toying with the idea of an ash glaze that ran and pooled but had the color of a celadon blue. The first idea was to simply try adding small increments of cobalt to my base glaze, I was fairly certain this wasn't going to work but I had to try. These are .1%-.5% though I'm fairly certain that those measurements are not entirely accurate. I mixed 100g test batches which means I was trying to weigh 1/10 of a percent for the cobalt. Eh, what can you do. I have a few different ideas but I'm really trying to keep the number of materials in the formula down to 4 or 5 ingredients. I like things simple, I hate it when a glaze formula has 17 ingredients in it. Just a personal choice.

That formula for anyone interested is:
4 Wood Ash
4 Potash Feldspar
2 Ball Clay

Back to work.


Joe and Christy said...

Brandon looks good. Before I left North Carolina for Wisconsin I was glazing everything bisqued. 4,4,2 was by far my favorite glaze. I'm also with you on keeping the number of ingredients to a reasonable number. Much past five ingredients my head starts to hurt. I've always admired the celedon blue glazes as well, though I've never done any serious testing in that area. I'm curious to see what you come up with. Good luck.

Scott Baker said...

Hardly my area of expertise, but could the color change be something as simple as different wood ash causing different results? Hard wood vs. Soft wood, etc. Just a thought.

brandon phillips said...

yes it could but-i've been using mesquite ash exclusively from the same source since i started(betty roses bbq). it can make a difference where the original tree came from, black dirt vs. red dirt can make a huge difference. more bark vs. less bark, etc. all or things out of my control. luckily the surface has never changed, just the color and tone which is is really an "easy" fix. i do know for a fact that my ball clay has more iron in it than it did a few years ago but since i add iron to the glaze anyways it's not an issue.

bryce brisco said...

hey...i don't know if you have a ballmill available, but i have recently been doing research on cullet. Making your own is really easy, crush up some budweiser bottles and ball mill for about 8 hours, sieve to an even mesh (usually 40m will take out the big chunks)
my recipe is:
33.3 wood ash, unwashed
33.3 local red clay (basically red art, which comes from ohio anyway)
33.3 budweiser cullet
2% RIO

makes a very nice glaze, very reliable, and very simple.looks good in salt or wood, cone 10-11.

Ron said...

Traditional potters in NC used cullet. That with ash and clay only I think. See Turners and Burners by Terry Zug. I've always liked your ash glaze Brandon.

paul jessop said...

Thanks all intreasting stuff