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About Min

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    full time potter / moderator

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  1. Min

    Majolica Clay Body

    Not trying to complicate things but if you are open to a different West Coast supplier the D'Arcy Redart clay from Tacoma Clay Art Center is a lovely clay to work with. Very smooth and forgiving. Deb's clear fits. A friend of mine uses it with slips, bisqued to 06 and glaze fired to 04, the red earthenware pots in her gallery are D'Arcy's. The body was devoloped by D'Arcy Margesson and comes with or without mica, he uses it for both majolica and slip decoration.
  2. Dollies and rolling carts, if it's heavy and it needs to be moved get it up on wheels. Save your back. I would also have started off with my wheel raised to standing height.
  3. Calculated COE figures don't work with any glaze with a crystalline structure, including the magnesium mattes. If you still get cracking with either of the above recipes try calcining part of the kaolin. For now I would just look how the glaze looks / tests after firing. If you are using the same glaze as a liner I would really suggest trying to cutlery mark it, might have to compromise between the degree of matte to gloss to prevent it. I used Dover White throwing body years ago, used low COE gloss glazes, had to get the COE below 6 to prevent crazing for the clear.
  4. Do you have any more info about the tea cup? Really can't give suggestions without knowing if the cup is made from low fire, mid range or high fire clay. If you don't have that info then the safest thing to do would be to low fire it so it doesn't melt or distort in the kiln. Problem with that is if the cup is mid or high fire clay then it literally won't hold water when low fired so it would only be suitable for decorative purposes. Commercial glazes are available either at your local ceramic / pottery supply store or online. Perhaps the place where you will be firing your cup has glazes also? Has the cup already been fired once with no glaze on it or is it unfired dry clay?
  5. Micro-crystals formed during the cooling of a high calcium or magnesium matte glaze will cause mattness, with a slow cool. Silica:alumina ratios can and often are higher than 5:1. I've found high alumina mattes often cutlery mark and prefer mattes from higher levels of the former mentioned fluxes. Silica:alumina ratio is an indicator of the degree of gloss but it's not the only factor.
  6. If you take the revised recipe that OCMI_Designs posted and drop the silica and bump the EPK to 26, and keep everything else the same you will get a very similar glaze to the one Bill posted but with about 1/2 the LOI than the Plus Six recipe. (part of the EPK will likely need calcining) Just another way to approach it.
  7. Min

    Lucy Rei Glazes?

    @Magnolia Mud Research,thanks for posting your ^3 Bronze recipe, I realize you and Terri both know it's not for food surfaces but in the event someone in the future reads this thread they should know that glaze is not food safe and to avoid the kiln fumes when firing.
  8. Min

    Favourite craft show tools and tricks

    Something super simple but took me years to think of is using little paper bags instead of newsprint to wrap mini pots in. I make 4 types of mini pots, used to wrap each one which was really time consuming, way faster just using little paper bags, especially when someone buys them in multiples. I've started using paper lunch bags for mugs and things of that size too. (I still bag their purchases so they can be carried easily)
  9. Min

    Glaze is pinging

    Just because both your clay and glaze are meant for earthenware temperatures doesn't mean they will suit each other. The glaze needs to fit the clay in order to avoid crazing (or shivering). What fit is measuring is called Coefficient of Thermal Expansion (COE or CTE) and is the difference between the COE of the glaze and body. When you read about clay and glaze “fit” an easy way for it to make sense is to think about how clothing fits. You are the pot and the glaze is a pair of jeans, they need to fit each other. If the jeans are too small they will stretch then tear, in ceramics this is called crazing. The glaze is under tension and crazes. If the jeans are too big for you they won’t fit either, they will not stay on. In ceramics this is shivering, the glaze is too big for the pot. The glaze is in compression and shivers (sharp slivers of glaze pop off of the pot). A little bit of compression makes for a strong pot but too much isn’t good. It’s especially important to have a non crazing glaze with earthenware. The glaze is what is keeping moisture, oils etc from being absorbed by the porous clay. With commercial glazes it's going to be trial and error to find a glaze that fits your claybody. I would start by asking the clay supplier for their recommendations for a non-crazing well fitting glaze for the clay you use and make sure you fire to the recommended cone.
  10. The G2934Y matte glaze with the G2926B clear added on Digitalfire is using 9 parts of the matte to 1 part of the clear. It sounds like you are using 10 parts of the matte plus 1 part of the clear? Added to this you are adding 10grams zirco to the matte. In any event I think you could decrease the % of the matte glaze, and increase the % of the clear, to help with getting a smoother surface. I would run a line blend with the matte and the clear, go from 50 matte : 50 clear up to 90:10. To keep the zircopax as a constant, put 10 zircopax in both the matte and clear bases. Have you tried cutlery marking the glaze? Might need more of the clear gloss glaze added to it to make a good liner glaze. With all the clay in the matte recipe it's going to appear quite thick compared to say a heavily fritted glaze with little clay. If you dip 2 test tiles with 1, 2 and 3 layers of glaze then when they're dry scratch through the glaze on one of the tiles so you can see the thickness, don't fire this tile. Glaze the other test tile the same way (with out the scratch) and fire. Keep the unfired tile as a reference to glaze thickness.Mugs below are dipped in my white glaze with 73 matte: 27 gloss (plus tin and zircopax). The glaze is still quite matte, it does crack on the handle joins if I don't use the wet brush technique before dipping.
  11. I use a blend of a dolomite matte with a lot of clay in it blended with a clear also, had the same issue. What solved the cracking was to use a fine paintbrush and brush water onto the handle joint and spritz water inside the mug bottom then let the mugs (or tubs etc) sit for a couple minutes then glaze. I'll do a whole board of mugs this way, dampening the areas where the glaze pools so it goes on thinner in those problem areas.
  12. If you run the wire under the pot more than once this can happen, just one pass of the wire is enough. Welcome to the forum!
  13. Min

    Help with firing programme

    Thats fine, just get it as flat as you can. I make mine very thin, like 2 -3 mm. Are you going to glaze the piece or ?
  14. Min

    Help with firing programme

    I think the firing schedule Beth Cavener uses could be adapted to your sculpture. I would skip the drying ramps but start with an overnight candling of the kiln, 10C up to 80C and hold overnight. For the firing change her top temperature of 1148C to 1000C (if you want to go to bisque temperature). I would also add a ramp 4 in the firing schedule to slow down the firing towards the top. Rate 3 would go at 90C to 700C, 0 hold. Rate 4 would go at 42C to 1000C. This slower rate of climb allows for more impurities to burn out from clays containing them. I would do the cool down rates the same as the Cavener schedule. Yes, it's fine to fire different claybodies together in the same load. The other thing I would do when firing your sculpture is to make a thin slab to fit underneath the sculpture from the same clay it's made from. Dry it between boards so it stays flat then put it underneath the sculpture so when the sculpture shrinks during firing it will shrink with the waster slab and not get hung up on the kiln shelf. When you go to glaze fire the piece use the same waster slab underneath it again. Welcome to the forum!

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