In response to several questions about the last Techno Tip. Tony has writen infor- marion on the Floating Blue glaze. Floating Bluc. probably the most well known and poplar cone 6 glare, was popularized by James Chappell inthe book The Potter's Complete Book of Clay and Glazes. Like most other glossy Gerstlkey Borate hased glazes, this ome uses nepheline syenite, silica and kaolin. Fired effects produced hy this recipe are a testament to ihe variegating effects that 45¢ rutile imparts to colowred non- opacified boron glazes. The term ‘floating’ could refer to two possibilities: The blue cobalt coloured surface appears to float on a translucent brown gloss layer. This layer is visible Where the colour breaks to brownish hues on thinner sections at edges and irregularities in the surface, More likely, however. it refers toa white opales- cent ‘boron-blue’ crystalline layerthat can appear to float over the cobalt blue back- ground. Cappell says this effect is “remi- niscent of a deep pool of water.” An amazing thing about this recipe is that ttactually has the potential to produce sax separate roechanisms of variegation: * Its colour and opacity vary greatly with thickness so it highlights irregularities in the surface, * ‘Phase separation’ in the translucent matrix makes the colour ‘swirl’ as small rivulets of more fluid glass flow around Mere viscous phases. * Titanium erystals in the matrix make it sparkle. *Calctum-borate horon-blue crystals grow on the surface. * Bubbles of escaping gases create pools of lighter coloured glass surrounded by darker rings. * Small black speckles are produced by unground particles of iron common in Most grades of red iron oxide. In addition, people commonly employ a vaniety of methods to increase the varia- Mioareh hrukd Floating Blue with Borag 2 TECHNO TIP by Tony Hansen FLOATING BLUE GLAZE tion of surface colour (1.2, sippling a sec- ond layer, brushing on a wash of another colouring oxide, double dipping. applying a wash of rutile, ete.) Anyone who has used thas ghize will tes- tify to the fact that itis fickle us Chappell notes, Among the many recommendations he makes on how tu use it he says “Don't substitute any oher chemicals for those given.” Well, that is exactly what we have done, Borag | isa Gersiley Borate substi- lute available from Plainsman Clays and its dealers. It is thoroughly documented at www. gerstieyborutc.com. Boraq 2 (84 parts Borag | with § dolomite and 8 whit- ing) works well in flowing blue. We have done a flow test to determine an exact melting comparison: the two are identical in Colour and fMurdity, Floating blue is a testament to how unique Gerstley Borate was. Floating Blue de- pends on the GB to suspend it (since there is only 5% kaolin) Try using a frit and it will settle to the bottom of the bucket like a rock, In fact, by using Borag 2 you can not only achieve the same colour but also wou will have a glaze (hat has even better application qualities. Gerstley Borute was the main reason for the unique visual appeal of this glaze. People who have tried to substitute frits have found their results lack one or more of the mechanisms of yanegution amd are more colour sensitive to firing tempera- ture and thickness. This is a testament to the fact that while glaze materials do have Flowing Blue with GB achemistry that can be matched by blends of other matenals, they also have a miner- alogy and particle size distribution that can play a big part in bow they melt and hehave in amelt of other things, A frit has i homogencous chemistry across all the particles whereas GB was a mia- ture of particles of radically dif- ferent chemistries and mineralogies. For more infermation, visit website: hitp:/digitalfire.coms geratlevboratefisanbluc. shite Techne Tips are wriffen by Tony Hansen with the support af Plains- man Clays Lr in Medicine Hat, Greenharm Potters Supplies, Sur- rey and Vancouver Islaned Por- tery, Nanaine are local affiliates, pottery galore --- and more / a | 264-dth Avenue Pane George. BC Val a4 250), 563 3880 New Management Actively seeking potters interested in selling their work on consignment or selling at wholesale. Please contact Sandra Stinner 250.563.3880 or K&B Pottery Galore & Mare 1264—tth Avenue Prince George, BC W2L 3]4 250.563, 3880