As most know, | am @ big proponent of understanding the chemistry of glazes in order to get control of them. However there is asituation when itis quite practical to take a material blending approach. This is when you have a material that already has a chemistry typical of glazes and fires as almost acomplete glaze by itself. In this circumstance you can simply add flux to melt it better, and opacifiers, colourants, and variegators to control the nature and colour of the glaze surface. At Plainsman we have been working ex- tensively on two materials and I thought you might like to know a litte more about them. Ravenscrag Slip This material has been available for some: years now and itis taking time to getit into the mind-space of potters and companies generally oceupted with textbook recipes, It is not typical of any other material cur- rently out there so this is likely part of the reason. Its claim-to-fame is mainly two fold: * [tis possible to use it 100% to create a silky to glossy glaze at cone 10 because it contains all the feldspar, silica and clay needed amd these are supplied in majority from the natural clay. *Itimparts beautiful working properties to the glaze slurry; it suspends if and im- proves evenness of application, drying speed, reduces shrinkage and cnables multi-layering (many of the most beauti- ful art glaze effects can be achieved by layering one glaze over another). We have registered a website at www ravenscrag.com and Kat Valenzuela from the lab at Plainsman has been authoring tt, She has been doing a lot of very interesting glaze formulation work in the past year and the recipes and com- ments are recorded on the site. In addition to some of the nice multi-layer effects, you will find one glaze in particular, a blue cone 6, to be quite stunning. I think itis a worthy successor to floating blue because it lacks its persnickety nature. If you want July/August 2003 Techno Tip Alberta Slip and Ravenscrag Slip by Tony Hansen to dabble in developing your own glazes, this is a great place to start What's exciting is that Ravenscrag is at hone in high, medium and low fire glazes, At high temperature it can be used as-is with additions of colour, opacifier, ete to create glossy and matte glazes. At middle temperature, 20-30% frit seems to work well, Atlow temperature 50-60% is needed, Frit 3195 at low fire produces a very at- tractive silky matte surface having a na- ture that is much more lively than the typical toilet-bowl type low fire glaze we are used to. We have made a change in the Ravenscrag Tecipe starting with mix number 4288 from May 2002. Itnow has 10% added calcium carbonate to make it melt better. If you have a material with a code number whose first four digits are lower than this, add 10% whiting to get the sare results as on the website, Alberta Slip We have made this material for many years as a substitute for Albany Slip and it is established in the market place across North America. You can use it at 100% to create a chocolate brown glossy glaze at cone 10 (but there is a problem with doing this, as we shall see in a moment). Many Albany glazes are based on the addition of an active flux that increases melt fluidity so much that greenish and yellowish crys- tals grow on cooling to completely change the character of the surface. Many black glazes are also hased on Alberta Slip, since it already contains lots of iron you only need to add a litte more and some extra cobalt or manganese, Lately we have done a number of produc- tion tests to develop a different version of this material. The major problem is that it is more much plastic than the silty Albany and glazes containing high proportions shrink excessively during drying and thus tend to crack. In fact is impossible to use Alberta Slip at 100% without calcining part of it for this reason. In version II we have replaced one of the plastic ingredi- ents with the main silty Saskatchewan clay Potters Guild of British Columbia Newsletter in Ravenscrag Slip. We have also fine- tuned the mix a little to better match the chemistry of Albany. The result is a new Alberta Slip Il thar is great to work with. It has very close tothe same melt fluidity and will likely be a one-for-one substinute (al- though we may put in a little more iron), However the real bonus is that version II can be used 100% to create a slurry that is a joy to work with and does not shrink and crack during drying (unless itis Very thick). It fires as a deep almost Tenmoku glaze at cone 10. The variegation and character of the surface is actually quite stunning in reduction. [| am going to use this as the glaze for a line of Medalta bean crock reproductions I want to make (Albany was the glaze likely used on the originals). The plasticity of Alberta Slip | (which will continue to be available) is good where smaller amounts ate used since it can a- sume the burden of suspending the glaze. However this new material really shines when it makes up the majority of the glane. In the Plainsman Studio we are having such good success that Kat and | are using less and less non-Ravenscrag non-Alberta Slip recipes all the time. In a few years I would not be surprised to see therm com- pletely take over the studio, If you would like a sample of either of these materials, please bet our dealers know so they can have them in stock for you. More information is available by visiting ww. ceramicmaterials. com and search for Alberta or Ravenscrag. These will also have links to other pertinent pages at Plains- man Clays website and others. Tony Hansen Digitalfire Corp. Techno Tip is generously sponsored by Plains- nian Clays Linuted in Medicine Har, Alberta, and ingffiliares in Frrich Colenbia, Greembant Poaners Supply Limited and Vancouver istand Porters Supply.