Sunday, April 22, 2012

Colour Tests

Wow, it has been a long time since I posted!

What can I say, Life has been happening. As it does.

I've been very busy getting my new pottery sale, fireGifts, organized. The hall is booked... the plans are made.... almost half the available spaces are already spoken for.... I'm getting excited! The sale is called fireGifts, as you may have guessed, and will be in the RA Centre, Ottawa over the weekend of Oct. 26-28, 2012. There'll be 40 clay and glass artists. The best, mostly functional, work in Ottawa will be there!

Got a speeding ticket, asked mildly if Ms. Officer was really sure she stopped the right person (she hadn't) and then got a ticket for driving with 'an obstructed windshield' due to having a small crack right under the mirror plus a red paper sticky in the lower right-hand corner. OK, I have to get that fixed anyway, but cheeeezz. And she's still wrong and the red sticky stays.

Ran around every day turning greenhouse and seed-starting-shed heaters on-off, on-off as the weather went from +20C top -05C and back and around again and back again.... we've had a few amazingly warm days, and many quite cold nights. Lots of things are going to bloom with brown frozen tips. Some of the early Daffodils lasted less than one day. This seems like Global Warning, not Global Warming.

Tried hard to fix my kitchen sink drain. It was clogged and I did get that fixed, but then when I went to put it all back together one of the rings that screw stuff together cracked and I couldn't get it all completely watertight. Then I tried to buy a new ring.... and discovered that it wasn't supposed to come off and only had because it was cracked, and the whole assembly has to be replaced. Ok, cue a plumber. I'm not up to spending hours hacksawing and glueing and fitting ABS pipe.

Kept trying to make stock for the coming Market season but I'm not sure I got much done. Luckily Super Helper was here and she did a lot of work testing various glaze colours. I would like a good blue and a good green, but it isn't easy. We used a system I learned years ago in a workshop. It's a bit tedious to do, but is a good way to narrow down what colourants to use and in what amounts.

For those who are interested, here is what you do:

1. Decide which base glaze you are going to use.

2. Decide what colourants you want to test. I wanted to test varying amounts of Cobalt Carbonate with and without Red Iron Oxide, Rutile and Superpax.

3. If you want to test 7 colourants, as I did, mix a batch of the base glaze 7 x 7 times the 100-gram amount. In other words, to test 7 colourants, mix 49 times the 100-gram amount of the base glaze.

4. Divide it into 7 equal amounts. (SH eye-balled and then weighed.)

5.For each of the additions you want to test, multiply the percentage you want to try by 2 and then by 7 to get the amount to add to each of the containers from step 4. I wanted to see what 1.5% Cobalt Carbonate would do, so we added 2 x 1.5 x 7 or 21grams of Cobalt Carb to container #2.  Container #1 was left with no additions, containers #3 to #7 contained, in this case, 42 grams of Cobalt Carbonate, 56 grams of CoC, 70 grams Red Iron Oxide, 112 grams Rutile and 112 grams Superpax.

6. Divide each of the 7 containers into 7 smaller ones. We used plastic cups. Number them as you see here.

7. Get matching test tiles ready, numbered as shown.

8. Now place one cup labeled #1, one labeled #2, and so on in a row at the top. Dip tile #1 in cup #1, #2 in #2 and so on.

9. Now pour a second cup labeled #1 and a second cup labeled #2 together. Pour back and forth a few times and stir to mix well. Dip tile #1-2 in this cup. Now do #1 and #3 together, then #1 and #4 and so on. This is your second row from the top. Keep going until you have all the combinations done.

Here's what you get: In the top row are all the tiles with double the amounts of colourants you wanted to test. The second row down is each of these mixed with an equal amount of the base glaze with no colourant, ie the actual amount you wanted to test. The third row is #2 plus #3, etc. Now if you like one, you just check the number on the back and you know what colourants in what percentage gave you that result.

Of course we tested 3 base glazes, and tested all the combos on two different clays. No point in not overdoing things!

This set of tiles is about the best of the lot. My usual base glaze on my usual porcelain clay. I really like tile 3-5, but it isn't blue, it is green! Tile 1-6 is nice too and will be worth more testing. As for blue, I'm still not happy and will have to do tighter more controlled tests around 3-6 and 3-7. I'm looking for a lively but not eye-popping blue.

Now, next week, can I please make some pots???