Cone 6 Wine Red Glaze

I promised glaze recipes earlier in this blog so here is my new favorite glaze. The recipe was first printed in Clay Times in the March/April 2005 edition by Richard Burkett. His recipe included the addition of .25 cobalt carbonate but without it, it's a beautiful wine red breaking white where thin. Thinner coats of glaze produce a mottled wine and white surface. Thicker coats produce a more solid colored wine. The glaze has not run for me and has a nice semi-gloss appearance. Slow cooling has little effect on this glaze but will change the color slightly to more of a burgundy than red. My test firing was done in oxidation and I do not know what the results would be in reduction.

32  Silica (flint)
21  Gerstley Borate
20  Calcium Carbonite (whiting)
16  Nepheline Syenite
11  EPK (kaolin)
5    Tin  Dioxide
.15  Chrome Oxide (chromium green)

Achieving Opacity in Glazes

I made my trip to stock up on raw materials and clay yesterday and was floored by the increased price of tin! It was more than double the cost of what I paid last year. Tin is used as an opacifier in glazes and also to achieve reds and pinks in midfire glazes. Due to cost, I've decided to save my tin for chrome-red glazes and substitute other opacifiers in various glazes. I've spent the morning researching my alternatives online and in Robin Hopper's book "The Ceramic Spectrum." The following link to the site Digital Fire had a pretty good list of opacifiers and covered most of what was in Robin Hopper's book. However, Hopper also mentions that Clays and Feldspars may act as opacifiers as well. These work similar to one another as a glaze will only absorb so much clay before the remainder remains unmelted. The glazes made in this manner would have an opaque matte character and may have a dry underfired look. I prefer matte glazes achieved by the formation of small crystals formed by slow cooling. Some of the materials that aid in the process are: lithium, barium (I prefer not to use this for toxicity reasons), zinc, potassium, magnesium, sodium, and iron. 

Glaze Simulator Website

Here's another awesome link to a free glaze simulator website. It enables you to enter your glaze ingredients when developing glazes and it will analyze those recipes for you: http://www.glazesimulator.com/

I also strongly recommend the following site if you fire to midrange cone 6: Electric Midrange Cone 6 Potters http://cone6pots.ning.com/ The following discussion is truly worthwhile no matter to what range you fire:   "How to direct your pottery knowledge to a business"

Bill Van Gilder Cone 6 Glaze Recipes

Happy New Year Everyone! I apologize for not posting for awhile but it has been a busy holiday season. Here's a link to some glaze recipes that Bill Van Gilder has generously shared. I am firing a test tile of his Crocus Martis Red today. I used red iron oxide in place of crocus martis. I'll let you know how it goes. I have been searching for a good cone 6 red glaze and would be very appreciative if anyone has a good recipe and would like to share.

http://www.vangilderpottery.com/glaze/vangilder%20CONE%206%20OXIDATION.pdf

UPDATE:
Well, it turned out to be a beautiful brown glaze with small reddish crystals. I've tried firing to cone 6 and then slow cooling to 1650 degrees Fahrenheit and holding for 30 minutes. I also tried re-firing to 1650 and holding for one hour. The glaze coloring remained the same for both tests. However, the slow cooled firing produced a semi gloss glaze and the re-fire produced a matte appearance. It does look beautiful with the wine red glaze though so it's definitely a keeper. I intend to pick up a Spanish red iron oxide or crocus martis at a later date and use that in place of the red iron oxide to see if it makes a difference.