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Member Since 08 Feb 2012
Offline Last Active Yesterday, 07:49 PM

Posts I've Made

In Topic: Water Seeping Through

Yesterday, 07:50 PM

Have you tried firing it even hotter than ^6? Like up to ^7 even though it's a ^6 clay?  IMO it's worth a test (use a waste tray/shelf underneath just in case)


You mention you "can't see any crazing"....to a molecule of water or a tiny bacteria, a teeny tiny fissure in the glaze is like the grand canyon, of course it will make it's way through!

If your glaze is crazed, the glaze and clay body do not fit one another, their coefficient of expansion is too dissimilar.  This is only part of your problem, the other seems to be lack of vitrification in the clay itself.  For those experiencing seeping on thicker forms - this is because the thicker it is, the more heat work it requires to penetrate the core of that clay mass and bring it to full maturity - which is why reducing thickness via trimming the foot resolved the problem.


To test if your clay is vitrified: fire object and then weigh it.  soak in water for 24hrs, dry it off as best you can and then weigh it again.  calculate % of absorption from the difference.

In Topic: Glaze Dripped Onto Kiln Floor

Yesterday, 07:23 PM

I've personally never seen a glaze drip go all the way through a soft brick, even though it's possible.  Usually you would catch it and give it attention, or kiln wash over it and neutralize the fluxing materials.

I HAVE, however, seen unchecked glaze spots eat all the way through kiln shelves.  Top of the shelf just kept getting washed over, but the glaze was still in the core and progressively made its way all the way through and formed a drip.  I think I saved it in my pile of treasures somewhere...

In Topic: Pestal And Mortar Machine

Yesterday, 07:19 PM

^yes, but then you have the dust hazard when grinding dry powders....



I recall the ball mill posted in the youtube link -- looks like a great DIY solution!

Another cheap alternative might be a Harbor Freight rock tumbler.

In Topic: Fixing Broken Pot

10 October 2016 - 04:10 PM

Any CA glue should work (cyanoacrylate aka super glue, krazy glue, etc) but a 2-part epoxy is technically stronger, but harder to control/wield/apply.  

I'd just use the CA glue in this instance.


You can mix all sorts of materials in with adhesives.  Whether it actually improves the surface afterward is highly subjective.

In Topic: Quartz Inversion

10 October 2016 - 04:02 PM

Well yes, the more mass in the form, the more they are susceptible to the forces of nature/physics/kiln firing/etc.  Hard to give specifics since it varies so much depending on what it is, how it was made, etc etc.


As for quartz inversion - 2% expansion doesn't seem like much to a little cup or plate, but to a 6ft tall sculpture with a 1" thick wall will definitely have some concern and you may have to make some big changes to accommodate making that item.  With bigger work it's inevitably going to be "moving more" as things shrink especially.  You actually have to engineer your sculpture to accommodate certain shapes, kiln firings, etc etc.


For example, everything made from clay will shrink to some degree and obviously clay can be heavy.  You may not be able to perceive the shrinkage from your average cup/mug, but if you scaled it up to a 24-36" diameter vessel you're definitely going to be able to see the shrinkage as it will be obvious at this scale.  Big heavy sculpture often gets vertical cracks originating from the foot, likely due to the heavy weight of the form and the friction on the work-surface as the piece dries, this continues as it fires and shrinks again.  Big work makes "walls" in the kiln that make heating uneven sometimes, so how you stack your kiln will likely effect the work too.  Example of that might be firing several long-necked forms - if you cannot place these centered in relation to the heat source, it's likely the uneven heating will warp the piece and it will lean toward the heat source since that side shrinks more.


If you fire very conservatively your chances of surviving these forces are much much higher.  Obviously you won't be able to fire big stuff on a fast kiln firing schedule, sometimes you even have to down-fire your work so it doesn't get dunting cracks. Keep in mind that my studio operates outside the box of your typical ceramics studio.  Most of our work is fired earthenware temp, with a forgiving stoneware clay body...oh yeah and did I mention most of our stuff is once-fired?!  Most of my gas kiln firings with big stuff takes about 1 week turnaround for firing - 1-3 day drying/pre-heat, up to 24hrs to fire, 2-3 days to cool.  Go slow from pre-heat to quart inversion.  Remember, it's not only quartz inversion to be concerned with...all ceramics still have chemical water that needs to come out too...so if you go too fast with a 1" thick piece of clay...boom....