Think the idea of mixing your own glazes is dead? Nope!
These are two pallets (of three) that went on a semi-trailer load to a Plainsman Clays store in Edmonton this week. They are packed with hundreds of bags of powders used to mix glazes. More and more orders for raw ceramic materials are coming in all the time. Maybe you are using lots of bottled glazes but for your cover and liner glazes it is better to mix your own. And cheaper! And there are lots of recipes and premixed powders here to do it. One of the big advantages is that when you dip ware into a properly mixed slurry it goes on perfectly even, does not run and dries on the bisque in seconds. No bottled glaze can do that.
Context: Where Do I Start?, Glaze Mixing
Sunday 13th May 2018
Mel Noble at Plainsman Clay's Ravenscrag, Saskatchewan quarry
Plainsman extracts 6 different sedimentary clays from this quarry (Mel knows where the layers separate). The dried test bars on the right show them (top to bottom). The range of properties exhibited is astounding. The top-most layer is the most plastic and has the most iron concretion particles (used in our most speckled reduction bodies). The bottom one is the least plastic and most silty (the base for Ravenscrag Slip). The middle two are complete buff stonewares made by mother nature (e.g. M340 and H550). A2, the second one down, is a ball clay (similar to commercial products like OM#4, Bell). A2 is refractory
and the base for Plainsman Fireclay. The second from the bottom fires the whitest and is the most refractory
(it is the base for H441G).
Context: Plainsman Clays, Secondary Clay
Saturday 12th May 2018
Ravencrag rutile blue vs. Alberta Slip floating blue at cone 6
Both have been applied at moderate thickness on Plainsman M325 (using a slurry of about 1.43-1.45 specific gravity
, higher values end up getting them on too thick). The Ravenscrag version highlights contours better (the edges are black because of the black engobe
underneath). It also produces the blue color whether or not the kiln is slow cooled to 1400F (although a faster cool is less blue). But the Alberta Slip version has zero cobalt so is less expensive to make. It produces a deeper color over the black engobe
underneath the upper section of the pieces. Both of these produce a wide range of effects with different thickness, bodies and firing schedules.
Context: GA6-C - Alberta Slip Rutile Blue Cone 6, GR6-M - Ravenscrag Cone 6 Floating Blue, Plainsman Cone 6 Slow Cool (Reactive glazes)
Sunday 6th May 2018
GA6A Alberta Slip base using Frit 3124, 3249 and 3195 on dark body
The body is dark brown burning Plainsman M390 (cone 6). The amber colored glaze is 80% Alberta Slip (raw:calcine mix) with 20% of each frit
. The white engobe
on the inside of two of the mugs is L3954A (those mugs are glazed inside using transparent G2926B
). The Alberta Slip amber gloss glaze produces an ultra-gloss surface of high quality on mugs 2 and 3 (Frit
3249 and 3195). On the outside we see it this glaze on the white slip until midway down, then on the bare red clay. The amber glaze on the first mug (with Frit 3124) has a pebbly surface that is not working nearly as well. These mugs are fired using a drop-and-soak
firing schedule. Some caution is required with the 3249 version, it has low thermal expansion
(that is good on bodies that normally craze
glazes, but risks shivering
on ones that do not).
Context: Ferro Frit 3249, GA6-A - Alberta Slip Cone 6 Amber Base Glaze, GA6A Alberta Slip base using Frit 3249 and 3195 on buff body, P300 and M370 mugs with GA6A Alberta Slip (using Frit 3249), Alberta Slip Cone 6 Base with Frit 3249, 3195, Plainsman Cone 6 Slow Cool (Reactive glazes)
Saturday 28th April 2018
Roasting Alberta Slip at 1000F
Roasted Alberta Slip (right) and raw powder (left). These are thin-walled 5 inch cast bowls, each holds about one kg. I hold the kiln at 1000F for 30 minutes. Why do this? Because Alberta Slip is a clay, it shrinks on drying. Roasting eliminates that, a 50:50 raw:roast mix works well for most recipes having high percentages of Alberta Slip. And 1000F? Calcining to 1850F sinter
s some particles together (creating a gritty material) while 1000F produces a smooth, fluffy powder. Technically, Alberta Slip losses 3% of its weight on roasting so I should use 3% less than a recipe calls for. But I often just swap them gram-for-gram.
Context: Alberta Slip 1900F Calcined, Alberta Slip 1000F Roasted, GA10x-A - Alberta Slip Base for cone 10 oxidation, GA6-A - Alberta Slip Cone 6 Amber Base Glaze, GA6-C - Alberta Slip Rutile Blue Cone 6, GA10-B - Alberta Slip Tenmoku Cone 10R, GA10-D - Alberta Slip Black Cone 10R, GR10-E - Alberta Slip:Ravenscrag Cone 10R Celadon, GA6-D - Alberta Slip Glossy Brown Cone 6, L3341B - Alberta Slip Iron Crystal Cone 10R, GA6-G - Alberta Slip Lithium Brown Cone 6, GA10-A - Alberta Slip Base Cone 10R, GA6-G1 - Alberta Slip Lithium Brown Cone 6 Low Expansion, GA6-AR - Alberta Slip Cone 5 Reduction Base Glaze, GA6-F - Alberta Slip Cone 6 Oatmeal, GA6-H - Alberta Slip Cone 6 Black, Calcine, Calcination
Saturday 28th April 2018
Twenty six bodies. Porcelains and native. Which do I like best?
I am testing runs of clays we (Plainsman Clays) make for potters. We are doing too many small-run products, bodies that we want to discontinue because others we are really good at making are much better. I am using native bodies and porcelains but the native ones will turn out best. I got lots of s-cracks on the porcelains, the low humidity at this time of the year caught me by surprise. But I got zero cracks on native bodies. And I am using engobe
s on the natives, these can turn even a dark colored stoneware surface pure white (I am also using a black engobe
here). I'll use a mix of base and cover glazes that I make myself (using recipes we publish) for food surfaces and decorate some using bottled commercial glazes.
Monday 16th April 2018
Absolutely jet-black cone 6 engobe on M340
This is the L3954B engobe
recipe but it has 15% Mason 6600 black body stain (instead of the normal 10% Zircopax for white). There is no cover glaze, yet it is durable and absolutely coal black (so a lesser stain % is possible). We have updated the mixing instructions at PlainsmanClays.com and Digitalfire.com pages (showing exact amounts for water, powder, Darvan) and the text on the glossary pages about thixotropy
s (read these again and learn to use the engobe process even better). This engobe base is designed to work on regular M340/M390 stonewares (not porcelains). This is exciting because these bodies are so much more robust in drying and much less expensive than porcelains.
Context: L3954B - White Cone 6 Engobe for Plainsman M390, M340, L3954B engobe page at PlainsmanClays.com, Engobe, Thixotropy
Friday 13th April 2018
Close-up of Floating Blue on cone 6 dark/buff burning bodies
Originally popularized by James Chappell in the book The Potter's Complete Book of Clay and Glazes. It is loved and hated. Why? The high Gerstley Borate
content makes it finicky. But the magic ingredient is not the GB, it is the rutile, Rutile makes the cobalt and iron dance. This recipe actually produces a number of different mechanism
s of variegation
. Color and opacity vary with thickness. Small rivulets of more fluid glass flow around more viscous phases producing micro-areas of differing colors and opacities. Titanium crystals sparkle and calcium-borate creates opalescence. Bubbles
of escaping gases (from GB) have created pooling. Small black speckles from unground or agglomerated particles of iron are also present. Surprise! This is actually Ravenscrag Floating blue. All the visuals, none of the headaches.
Context: Gerstley Borate, Rutile, GA6-C - Alberta Slip Rutile Blue Cone 6, GR6-M - Ravenscrag Cone 6 Floating Blue, G2587 - Floating Blue Cone 5-6 Original Glaze Recipe
Friday 23rd March 2018
Feldspar applied as a glaze? Yes! The way I did it will change how you glaze.
Custer feldspar and Nepheline Syenite. The coverage is perfectly even on both. No drips. Yet no clay is present. The secret? Epsom salts. I slurried the two powders in water until the flow was like heavy cream. I added more water to thin and started adding the epsom salts (powdered). After only a pinch or two they both gelled. Then I added more water and more epsom salts until they thickened again and gelled even better. They both applied beautifully to these porcelains. The gelled consistency prevented them settling in seconds to a hard layer on the bucket bottom. Could you do this with pure silica? Yes! The lesson: If these will suspend by gelling with epsom salts then any glaze will. You never need to tolerate settling or uneven coverage again! Read the page "Thixotropy
", it will change your life as a potter.
Context: Epsom Salts, Suspending pure feldspar and applying it as a glaze, Pure Custer Feldspar and Nepheline Syenite on cone 10R porcelain bodies, Thixotropy, Powdering, Cracking and Settling Glazes
Friday 16th March 2018
Making ceramic tile shapes by 3D printing your own cookie cutters
This was done on an affordable RepRap printer. The red plastic templates were drawn in Illustrator, extruded in Fusion 360 and sliced and printed using Simplify3D (which took about 30 minutes each). The round wooden block was used to press these cookie-cutters into the clay. The plastic wrap made sticking a non issue (and rounds the corners nicely). The clay is a low fire, buff burning talc body (Plainsman L212). Commercial bottled glazes were applied by brushing (in three coats) after bisque. The tiles were fired at cone 03. This is an old classic design that I discovered when researching Damascus tile. The toughest obstacle was learning how to use Fusion 360. It turns out that cookie cutters are a starter project for many 3D software packages, there are lots of videos on making them.
Context: 3D Printing Ceramics
Saturday 24th February 2018