Saturday, January 10, 2009

Even more Bentone EW

I tried to get the batch of 300 grams of dry materials, 1 gram of Bentone EW, and about 4 tsp of CMC solution to work with 175 ml of purified water and it did not. The brush dragged on the pot. It's not that it was too thick -- it just did not work very well.

So I say that, for me, 200 ml of water is perfect for brushing this particular glaze on to this particular pot.

If you have a different glaze or clay, or bisque hotter or cooler, this will be slightly different for you but this is a good place to start.

Thursday, January 8, 2009

The Bentone EW story continues.

Yesterday I mixed a glaze with .33% Bentone EW and 200 ml of water. The exact specifics are 300 grams of glaze, 1 gram of Bentone EW, and 200 ml of water. I also added about 4 tsp of CMC solution. 

It worked really well for brushing; in fact it was a little watery so today I am going to try to reduce the water even more -- probably 175 ml. The less water there is, the more glaze there is in the water, and the faster coats build up on the pot.

I'm still pretty amazed by how little clay there is in the glaze, how well it brushes, and how well it stays in suspension. 

Friday, January 2, 2009

Ice Crystal

Today I made some ice in the freezer of the fridge in the pottery shop and came back to find this ice crystal sticking out of the ice tray. It seems very curious to me that something like this would happen. How could this crystal grow an inch out of the water? I did have the ice tray full of water and that might have done something with the surface tension of the water so that this thing would grow. 

Thursday, January 1, 2009

Specific Gravity for Crystalline Glazes and Bentone EW

Someone recently posted a question on the Crystal Forum about whether there is a perfect specific gravity for a crystalline glaze. My answer to that is that there might be, but I think this is not the best way to see the answer to the question, "What is the best, most efficient way to apply crystalline glaze to my pot?"

I think you have to take a look at all the variables, learn what part each of them plays, and go forward from there. 

The first thing to look at is how are you going to apply the glaze. The conditions are different if you are going to brush the glaze rather that spray or dip it. I brush all my glazes and so the specifics here are going to be about brushing. But the generalities apply to spraying and dipping too.

Next you have the glaze itself and most crystalline formulas have very little clay which means that they are not really going to act very well no matter what, if you don't do something. But you can do something and the glaze will be fantastic to use.

I have been working with a material called Bentone EW and it looks like it is going to be the only clay that I will need in my glazes, and it also looks like the glaze will be really nice with only .5% Bentone EW. Imagine a glaze with .5% clay which stays in suspension and brushes well. 

According to my friend Andreas Widhalm, Bentone EW is 10 times as powerful as regular bentonite. Bentone EW is what will suspend the ingredients in the water. It's much more powerful than Veegum T or Bentonite or Macaloid. 

I mix up glazes in increments of about 300 grams dry materials. To this mixture I added 1.5 grams (.5%) of Bentone EW, dry mixed with a fork,  and then added 240 ml of purified water and this made a very brushable glaze with the addition of some CMC solution. I think I can actually take out some of the water and have an even better glaze. Next time I will try 200 ml of water. I was able to brush the glaze on much faster than ever before. 

One of the major points is that the more water you have in the glaze, the longer it will take to brush it onto the pot at the appropriate thickness. So, if you are smart, you want as little water as possible so long as the glaze brushes wonderfully. 

Adding CMC will help the glaze to brush well. If you feel like your brush is dragging on the pot, you either need more CMC or more water. Again, according to Andreas, if you want CMC to thicken a glaze use it at a molecular weight of 300 or greater  --- CMC with a molecular weight of less than 300 will thin a glaze. You really need CMC for brushability. 

Finally for each different glaze you will need a measured amount of water, added CMC -- I make mine as a solution, and Bentone EW.

As an upper limit on the Bentone EW, I have a glaze with 2% EPK and 1.5% Bentone EW. I have added about 500 ml of water to get it to brushing consistency -- it also has a lot of CMC  -- and I can brush and brush and nothing happens much except that the pot gets wet. Almost no glaze material shows up on the pot. I applied about 20 coats this afternoon and only got about .005" of glaze and that is not enough. I will have to throw that glaze away as it is useless. Its consistency is actually thick so don't let thick or thin fool you in how much water is in the glaze. 

And I guess that's why I feel like specific gravity is not the right way to look at this problem. Specific gravity actually is used as a measure of solutions and a glaze is not a solution, it's powder hopefully suspended in water, which, I guess, makes it a compound. 

I hope this helps. I would encourage you to keep good notes on how much water you have in each glaze batch, and how well that batch worked for you in application.