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Hello,

I have only been making my own glazes for a few months so I don't have all that much experience. What should I do to dispose of test glazes that did not work out? I know I cannot pour them down the drain or dump them in the grass as some have toxic chemicals in them. Any ideas?

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I have a dishpan that I wash all of my glaze bowls, stirrer, and brushes in.  I siphon off the clear water and then put the glaze sludge in a big jar.   I let that jar sit and dry,  when it is full I take it to the hazardous waste site.   Denice 

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small story about this: My outdoor sink exits under the studio slab and out and downhill through a PVC pipe under one of our planting areas by the house.

The water then exits into a swale and out to a field.

One year the PVC came apart and the sink dumped into the plant area where a tree was planted. By the end of the year the tree was almost dead...I believe from toxic water from glazes and clay.

After the pipe was fixed the tree revived.

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You can pay a hazardous materials company to properly dispose of the glaze materials but it will cost you. Last time I sent materials from the college to be disposed I believe it cost me over $1/pound of material and we had a "bulk" price because the chemistry dpt was also disposing at same time. Still cost around $800.  Cincinnati (where I live) hosts a number of "materials disposal days" (old paints, medicine, etc) where folks can bring in hazardous materials and dispose of for free. I do not know if they would take in glaze materials; likely they would, never tried. In the past what Ive done with smaller amounts of materials is to make (throw/extrude/hand build) a THICK (and I do mean thick, 1" or more) walled vessel, not terribly large (think tall narrow cylinders), bisque theses, and pour my waste glaze materials into these, let dry for a long time (big wet mass takes long time to dry, def. do not want to blow this up), then fire. I always "underfired" my glaze wastes a couple of cones; no need to take to maturity (not looking for pretty surfaces, just a good melt). Taking it to maturity just adds more stress on your waste vessel. Fire slowly until you get into red heat; dont blow this mass up. Also, put into a larger vessel in case you spring a leak during firing. Once fired you can dispose of the "waste log" into regular garbage as the toxic materials will be encapsulated in glass (granted your glazes produce a solid glass melt; if not, mix into basic high flint glaze recipe). This method works fine for amounts in the less than five gallon volumes; over that amount and you'd be making and firing so many logs it'd probably be cheaper to just pay a company to dispose of. It's a hassle but its a necessary evil to properly dispose of these hazardous chemicals; dont want them in our drinking water.

   Another option is to utilize your glaze wastes as a "trash" glaze. Sometimes you mix a number of test glazes together into one large batch and you get a very good looking glaze, oftentimes it ends up a ugly brown/black mess. However, if you dont want to just "throw away" materials you can Doctor the trash glaze a bit and produce a decent looking glaze. Additions of cobalt(powerful colorant, even in tiny amounts) will produce a nice looking blue'ish glaze.  DO NOT, and I mean DO NOT use trash glazes on utilitarian pots; inside or out. Its almost a guarantee that the glaze will have a poor fit to your pots, and will not be the hardest, most stable glaze that you'd want to eat off of. Use it for decorative pots, flower pots, etc. An idea I've been kicking around is making large tubes that I would glaze with our trash glaze and then fill with gravel and use as retaining walls around the property.

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hitchmss,

Do you think it would be helpful to fire the glaze log containers to maturity with a liner to help prevent any potential leaking? I've been considering something similar to this for some time now but have been too concerned about a kiln disaster. I fire at ^6. I have been thinking I'd make a container and fire it to ^6 with a liner glaze to seal it, then fill it up with trash glaze and  after LOTS of drying fire to ^3 to get a decent melt.  Do you think this would help? Totally unnecessary? Either way I think firing the container in an additional sagger vessel as you suggestied would give me piece of mind. 

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18 hours ago, Chris Throws Pots said:

hitchmss,

Do you think it would be helpful to fire the glaze log containers to maturity with a liner to help prevent any potential leaking? I've been considering something similar to this for some time now but have been too concerned about a kiln disaster. I fire at ^6. I have been thinking I'd make a container and fire it to ^6 with a liner glaze to seal it, then fill it up with trash glaze and  after LOTS of drying fire to ^3 to get a decent melt.  Do you think this would help? Totally unnecessary? Either way I think firing the container in an additional sagger vessel as you suggestied would give me piece of mind. 

If you fire a liner glaze first, the cylinder will no longer be porous to absorb the waste glaze and it will take forever to dry. 

Or, you could pour the glaze out in a puddle to dry first and fire the cylinder full of dried glaze.

Edited by Rae Reich

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Absolutely it would take a long time to dry. But wouldn't it take almost as long even is the vessel was only fired to bisque? Even with the vessel walls at 1" thick they it can only absorb so much water from the glaze before  the process relies on evaporation. I figure either way it'd be the type of thing where the glaze waste gets poured in then the vessel sits for a month or six weeks.

Pouring into a puddle and loading the cylinder with dry glaze sounds like a good idea. Break out the respirator!

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On 5/5/2018 at 7:03 AM, Chris Throws Pots said:

Absolutely it would take a long time to dry. But wouldn't it take almost as long even is the vessel was only fired to bisque? Even with the vessel walls at 1" thick they it can only absorb so much water from the glaze before  the process relies on evaporation. I figure either way it'd be the type of thing where the glaze waste gets poured in then the vessel sits for a month or six weeks.

Pouring into a puddle and loading the cylinder with dry glaze sounds like a good idea. Break out the respirator!

A glazed vessel will absorb no water from a glaze, so only the top surface exposed to air. Bisque will continuously absorb and evaporate. Either way, there will be much less volume of dry material when the water has finally gone - just a layer on the bottom in a glazed vessel, a coating on bottom and sides in bisque. Adding more glaze to dry at that point to fill the vessel will just wet all the contents. 

To avoid glaze dust, the nearly-dry puddle can be broken up and put in the bisque vessel to await additions until about half full. If you only fire to vitrification, ^06, it shouldn't put too much stress on the piece. 

Hope others will contradict me if my assumptions about glaze vitrification are wrong.....

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On 5/4/2018 at 10:51 AM, Chris Throws Pots said:

hitchmss,

Do you think it would be helpful to fire the glaze log containers to maturity with a liner to help prevent any potential leaking? I've been considering something similar to this for some time now but have been too concerned about a kiln disaster. I fire at ^6. I have been thinking I'd make a container and fire it to ^6 with a liner glaze to seal it, then fill it up with trash glaze and  after LOTS of drying fire to ^3 to get a decent melt.  Do you think this would help? Totally unnecessary? Either way I think firing the container in an additional sagger vessel as you suggestied would give me piece of mind. 

Chris; do not fire the cylinder to maturity first. The porosity of the vessel is not going to be a big advantage as you're gonna fill it full of glaze waste; its going to reach its maximum amount of absorption quite quickly. Its gonna take weeks to dry out; stick em in the sun or behind your kiln as you fire to make em dry faster. You dont want to fire to maturity with a liner for the simple fact that if you did, now you've got a vessel which has formed crystalline bonds  in the clay body (and clay/glaze interface) which are more sensitive to thermal shock. Even considering that you are going to fire slowly until you've gone through quartz inversion (red color), that's extra stress which can cause a crack...we dont want cracks.....think hole in septic tank.....ewww.....new kiln. The liner glaze will do you more damage if you dont put the liner on the outside too (coefficients of expansion), and if you do, its not gonna do you any benefit when it reaches maturity as its going to be back into glaze melt itself.

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On 5/7/2018 at 12:40 PM, Rae Reich said:

A glazed vessel will absorb no water from a glaze, so only the top surface exposed to air. Bisque will continuously absorb and evaporate. Either way, there will be much less volume of dry material when the water has finally gone - just a layer on the bottom in a glazed vessel, a coating on bottom and sides in bisque. Adding more glaze to dry at that point to fill the vessel will just wet all the contents. 

To avoid glaze dust, the nearly-dry puddle can be broken up and put in the bisque vessel to await additions until about half full. If you only fire to vitrification, ^06, it shouldn't put too much stress on the piece. 

Hope others will contradict me if my assumptions about glaze vitrification are wrong.....

Rae, you may be confusing maturation and vitrification. Clay bodies and glazes both have respective maturation points (temps at which they SHOULD be fired), the maturation point for clay bodies is typically where the clay body reaches vitrification (clay forms crystalline bonds) making it more glass like, and less porous. Some clay bodies NEVER reach vitrificaton even if fired at their maturation; A high iron clay body/earthenware (terra cotta flower pots, etc) will never vitrify because iron acts as a flux, and in those high percentages, that clay body, if over fired (over recommended maturity) in an attempt to vitrify, will melt the clay body and/or make it very weak due to over vitrification. Most clay bodies, even when designed to vitrify at low fire ranges, are still pretty porous in comparison to ^10 stoneware/porcelain.

   I would NOT suggest pouring glaze to dry out; the assumption is that you're pouring it onto something that is porous, which means then you'd have a porous surface which is covered/absorbed glaze wastes (extra work to clean). Leaving sleeping bears lie(more true literally and metaphorically in ceramics). Dust that is left undisturbed is "safe" dust; why go through making ANY extra dust than you need...EVER! Pour it into your waste log wet, and let it sit forever to dry; most of us have a bucket or more which has been sitting for months/years/decades; an extra few months for it to dry completely ain't hurting no body.

   You are correct, that as the water evaps you will have more room to fill up; top it off as you go!

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I referred to glaze vitrification. It seems like one would want to fire the waste glaze only to the point where it can no longer be reconstituted with water. That's the point I labeled (possibly erroneously) as glaze vitrification.  Maybe it's just quartz inversion.

Would anyone care to fire to glaze maturation a cylinder full of dry glaze material!?! Wouldn't that cylinder be stressed much more than one which was merely coated thinly with glaze? 

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On 5/16/2018 at 5:38 PM, Rae Reich said:

I referred to glaze vitrification. It seems like one would want to fire the waste glaze only to the point where it can no longer be reconstituted with water. That's the point I labeled (possibly erroneously) as glaze vitrification.  Maybe it's just quartz inversion.

Would anyone care to fire to glaze maturation a cylinder full of dry glaze material!?! Wouldn't that cylinder be stressed much more than one which was merely coated thinly with glaze? 

Depending on what the fluxes/feldspars are in your glazes, the point at which melt begins can vary greatly. All your recipes may be cone 10 recipes, but some fluxes may begin to melt at cone 7, and others may not begin until 9. Unless all, or predominately all your waste is the same recipe/flux, it would be difficult, without testing, to determine just how much heat is enough. I agree, no need to fire to maturation. Enough to enter melt is all you need; a couple/few cones shy of maturation is probably a safe bet. Aside from stressing the vessel with more heat, the combination of numerous fluxes/oxides can drastically alter the melt point.

There are ceramic surfaces (decals etc) which get fired to temperatures at/around quartz inversion (1064 F), but not many glazes do(some lustres, etc). 1064 would be around a cone 023/024. Quartz inversion is the state in which quartz particles go from an Alpha to Beta state (reverse upon cooling), and has little to nothing to do with glaze maturation. Ceramicists are concerned with the phase mainly in relation to the expansion/contraction which occurs at this state.

    Yes the cylinder would be more stressed filled with glaze rather than just coating the surfaces, but just coating a cylinder wont use a whole lot of glaze. Disposing of glaze doesnt accomplish anything for my other than cleaning up the studio and saving me paying someone else to do it; the less time invested the better.

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Thanks for the detailed explanation. 

I think if I had a quantity of hazmat-level (in the raw) glaze I would rather use it to glaze up some planters and get rid of it that way. Just don't like the idea of keeping a cylinder of raw glaze around until full and then firing it.

love to hear how that works out...

Edited by Rae Reich

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1 hour ago, Callie Beller Diesel said:

My municipality just accepts my 3 gallons of glaze waste at the paint/construction waste drop off at the fire station. The colourants and clays are often in paint as pigments and fillers.

Glad to hear that the drop offs will take it (hopefully my area will too!).

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