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The Newsletter for Raku Artists and Raku Art Lovers ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~- September 2004 Issue #23 Published by In This Issue ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ Welcome Just Raku Readers It is apparent that summer weather (at least in the northern hemisphere) is starting to turn cooler and people are starting to surf on-line again given the increase of subscribers (I broke 1200 subscribers with this issue), in increase in the sales of Got Raku? clothing (http://www.cafepress.com/gotraku), and sales of my Raku Glazes eBook (http://www.rakuglazes.com). Clay artists must be spending more time inside now (Like me!) I guess that means it is about time to start up the ebay listings again. I really slacked off over the summer, so I'll start listing again for the holiday season. This month we have a guest article by Chris Rundle (Thanks Chris!) This issue seems to be primarily focused on mixing glazes so enjoy! Remember I always look forward to your feedback, suggestions, questions, and article ideas at: mailto:editor@garyrferguson.com. Gary R. Ferguson ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ * From the Studio * I worked in a "Shampoo" Studio this month… There is going to be some "smoky" weekends coming up! ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ * Article * Converting a Glaze Recipe from Volume to Weight Lots of recipes are in volumetric measurements rather than
weights, which makes it difficult to make up a small batch to test
something. Anyway, volumetric measurements of powdered solids are inherently
inconsistent, because a given volume of a SETTLED powder weighs more than
the same volume of the same powder when UNSETTLED. Try it - a cup of lumpy
flour weighs more than a cup of sifted flour. So - how to convert a recipe in CUPS into weights and percentages... Take your "Blue Velvet II" as an example: OK, noting that the smallest volume is a Tablespoon, and
that there are 16 Tablespoons to a standard Cup, we can convert all the
volumes into "units" of tablespoons: Gerstley Borate 48 TBS (3 cups * 16) (or 48
"units") Now we need to weigh a standard measure of each ingredient -
I used a 5ml medicine spoon, but anything will do - a teaspoon, baby milk
scoop, etc as long as you use the same thing each time. You only ever need
to weigh things once if you keep your standard, so keep a record. Mine went
like this: Ingredient Avg. weight of 1 level 5ml spoonful
"unit" Now we can work out some weights: multiply the
"units" we worked out in the last conversion, with the weight per
standard volume we just weighed:
These figures are real weight equivalents for the volumetric
measurements in the original recipe. You can leave it like that, or finally convert to
percentages. To do that, add all the figures up (110.4 + 39.2 + 28.8 +
76.8 + 3.8 + 3.1 = 262.1) and divide it by 100 (= 2.62) Gerstley Borate 110.4 / 2.62 = 42.12% This is probably too accurate and can be rounded to the
nearest 0.5% (maybe to the nearest 0.1% for ingredients present in small
amounts?): Gerstley Borate 110.4 / 2.62 = 42% Now you have a Weight Recipe for Blue Velvet II. ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ * Tips and Techniques * Do you have a glaze that is a little too runny? Does is look great, but ruins kiln shelves? Well don't give up hope; you can typically adjust this glaze - even if it is a commercial glaze. You can add silica to a glaze, which will typically make it less runny by raising the melting temperature. You will have to experiment with different quantities to add depending on the glaze. I would start with 5% or 10% and see if that is enough. If it is still too runny add some more. Remember this may affect the glaze in other ways so test, test, test. ~~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~- * Q & A * Why Volume Glazes? You may have run across a volume glaze recipe (such as in the article above). A volume recipe is one that uses a volume (like Cup, Tablespoon, scoop, etc.) for the units of a recipe. Measuring a recipe in this manner is not as accurate as one measure by weight, due to the possible compaction of powder materials. So why do they exist? There are a couple of good reasons. First, not everyone has a precision scale to measure out ingredients. These can cost $100+ USD where a measuring cup may be less than one dollar. Second, speed. It is much faster to scoop out 3 cups of a chemical that it is to measure 500 grams of the same material. Third, it is easy mix different sized batches. If the recipe is recorded in cups, you can use any size container (larger or smaller) instead. 300+ Volume and Weight Raku Glazes can be found at: http://www.rakuglazes.com/ ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ * Glazing * Hi Gary, WOW! That glaze alone is worth the price of the book! It's
gorgeous! I have a slight problem with crackle white though - maybe you have some thoughts on it? It crackles OK, but it's a sort of cream/beige color - and what I was really after was a brilliant white. The recipe is as follows (it DOES make a consistent "Cream Crackle", if anyone wants one of those...) "Cream Crackle" Any ideas or suggestions for a bright white crackle? In regards to your "cream" crackle, it very likely
could be one of two things: If you are sure your clay is white, you might try reducing
the amount of Tin Oxide so it is more of a clear crackle instead of a white
crackle. ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ * Reader Feedback * * * * * * * * * * Hello Gary. I am just starting in ceramics & find the Raku pottery to be the most beautiful of all. I have tried many pieces & am not getting the results that I am looking for. First of all, I have not gotten a clear answer to how long to leave the pot in the combustible container before starting the reduction process. I have tried covering immediately, but the fire goes out before all of my material has burned & I end up with a lot of unburned newspaper & a black smoky finish on the pot. The last piece I did, I uncovered several times & moved the paper around to get it all to burn. Results were excellent on the bottom half of the pot, but the top half was black. As I said earlier, I am just getting started with Raku &
everything I have read, leaves out many steps. I have been to many Raku
websites & have found yours to be the most interesting with the most
beautiful finishes. Any help you could give would be greatly appreciated
& I will be more than glad to e-mail pictures of the results after your
suggestions so you could see how your advice has helped me through this
learning process. I would greatly appreciate any help you could give me
& all kidding aside, you do have the best-looking Raku pottery out
there. Keith C. PS: If you have a book that explains all of the steps in detail, let me know & I will be glad to order it, although it would be great to get some advise from the Master himself. Hi Keith: It almost sounds like you are either not heating the pieces enough in the kiln before you move them to the reduction chamber or you have too much reduction materials in the container. I usually remove my pieces from the kiln at around 1700F - 1800F. My reduction chambers are lined with sheets of newspaper, which catch on fire almost immediately. I will let them burn for just a few seconds before I put the lid on my reduction chamber. When I remove the piece from the reduction chamber, not all of the paper material has burned, but quite a bit has. I just leave it in there and add fresh to it for the next reduction. Also (I could not have planted a better question), I do in
fact have a new Raku eBook that is almost ready, that I will be letting you
all know about when I done. Stay Tuned… Hope this helps, * * * * * * * * * Hi Gary, Hello: * * * * * * * * * Gary, Jean: * * * * * * * * * Hi, Hi Jeff: If the matte glaze is rough, you might want to sieve the
glaze to remove the larger particles that don't melt in the firing. Also, for matte glazes, I typically reduce in sheets of
newspaper and try and keep the reduction materials off the piece. I leave pieces in a reduction chamber for 20 - 30 minutes
before I finish cooling with water. You might also try firing slightly hotter as well. (1750F or
1800F) Hope this helps. * * * * * * * * * Hi Gary, thanks for the note. I have some of Les Mitchell's
pieces which is the Rainbow I would love to get close to, the rim has
crackle white, it looks sharp. Do you have any further points or a glaze
name in your book that might come close? Thanks, have a great day, Jeff: I believe I have seen some of Les' pieces before and the
walls of the piece on consistently thin. This may allow the copper matte
glazes to perform better than a piece with thick walls or partly thick and
partly thin walls. ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ * Calendar * My show calendar for 2004 will probably be smaller than in the past. I only plan on doing two or three shows, but spending more time focusing on eBay sales. This way I can spend more time with the family and less time sitting in a booth. Nov - Beaux Arts Holiday Show On going eBay Listings http://tinyurl.com/tn08 ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ * Click Away * Sam & Christi McPeak Tim & Peggy Smith Michael & Michele Gwinup Just Raku Logowear Got Raku? It does a Clay Body Good! Just Raku Newsletter Archive ~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ This newsletter is send to opt-in members only. If this issue was forwarded to you and you would like your own copy each month send an email to subscribe@garyrferguson.com with SUBSCRIBE in the subject line. If you wish to no longer receive this newsletter send an email to unsubscribe@garyrferguson.com with UNSUBSCRIBE in the subject line. Disclaimer: Just Raku, the owner(s) and representative(s) of
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