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Terry V.

Biodegradable Cone 6 Clay

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I use Cone 6 clay and plan to make biodegradable cremation urns for a local funeral parlor.  I know I can simply not fire the vessels and they will biodegrade in water (ocean, lakes, ponds) as requested.  However, because they are so brittle when bone dry, I wondered if I could fire them very very low to give them some strength, but still retain the biodegradable capability.  Does anyone have any info on this option?

Terry V.

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I don't think it work's that way. Once you fire beyond the point where the clay starts to change from dried mud into a material where the quartz transforms, I don't think it is biodegradable. Perhaps someone could provide a more descriptive account of the molecular change that happens in the early stages of the firing process.

 

Marcia

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Having never fired clay to only 800-900F degrees, I honestly don't know if it would harden it at all, or if it would just be like it was before firing. You would burn off a certain amount of organic material, but I don't know if you'd get any sort of fusing at that point or not. Over 1000F you'll start to achieve permanence, but maybe not enough that it wouldn't still biodegrade. How quickly does it need to decompose? I think some test firings are in order.

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i've tested out slaking down clay that's fired up to around quartz inversion - to some degree it does break down in water, but not all the way like greenware does, but ultimately it does kinda slake down i guess (at least at the temp my clay was fired to).  the items had about the same strength as it would if it was regular greenware, so i'm not really sure if you'll get the strength you want to achieve by trying to fire the clay --- but every clay is different, and a hundred degrees in either direction could mean failure or success, so testing is definitely recommended.  

 

My best guess is that you may have to add some sort of binder in the clay to help give strength, yet still decompose.  Some of my immediate thoughts go toward clays with higher green strength - stuff like bentonites or ball clays.  Then you have tons of organic binders that can be added into the clay - stuff like CMC, PVA, starches (aren't water-friendly golf balls made from cornstarch?), beeswax or paraffin, shellac, etc.

 

What about encapsulate your regular clay body with something that'll resist water for a while (like wax or shellac), but will break down eventually enough to let water in and slake the clay?  You'd also be able to pigment that medium if you want color on your finished urn.

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I would think they have to understand that the bio degradation isnt going to be a fast process. Or really I should I ask what is the time lapse theyre looking for? A couple of days or a couple of weeks? years? I understand once its a ceramic material that turns into a thousands years but still. I would think maybe using a combination of binders and utilizing paper clay to really give the greenware some extra strength.

 

I think paper clay if having the right proportions could be a good strong choice. Still at the end of the day its going to have precious ashes of a loved one in it so I dont think theyre going to play hot potato or anything with the vessel.

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I think your answer lies in the prairies of the US. Here in PA even we can walk out into lots of fields and search in among the rocks and such and find bits of pottery shards that have survived the centuries. Sure, broken, but the texture of the makers decoration, and a smooth side is evident. How biodegradable must something be?

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Does the urn have to biodegrade, or is the important thing here that the ashes become dispersed in the lake? If it's really the ashes they're concerned with, make a regular lidded jar, put the ashes in, and glue the lid on with Titebond or some other water soluble glue. Leave a few of small holes in the jar just under the lip for water to go into so the pot doesn't float. Once the jar sinks down, the glue will soften and the lid will fall off, dispersing the ashes. The jar becomes a home for aquatic life.

Colby Charpentier likes this

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Not sure how you want to finish   the urn, but it won't be glaze if you want it to biodegrade. So why not just form the urn, let it dry, and paint it with a thick coating of PVA or maybe sodium silicate. Once it sets up it should have enough green strength to handle.

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Hi

 

I found a paper clay mix of 40% paper to clay ratio gives a strong pre-fired product that will hold its structure well if not thin walled. Adding PVA glue makes it stronger and gives it water resistance but not waterproof.

 

Have used this mix for childrens modelling material and, with sand, as a 'form now, fire now' raku body.  Dried it feels like clay 'cardboard', can be sanded and painted.  If used for your purpose would sand, paint and seal again with polyutherane.

 

Otherwise really like Neil's idea!... in terracotta which 'grows' mosses/algae/seaweeds for water creatures to live in when the loved one is gone.

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I think Neil and Bob have really good suggestions.

 

I will offer another.  I was given some blue-green found clay, that fires to a nice golden-yellow.  It threw well enough, and there were no issues with the firing, other than some minor dunting on one of the wares.  However, despite all this, the clay body was VERY porous, and even weak.  Prior to firing the wares, I made a small test tile, so that I could make sure the clay body would fire well, to begin with.  I could snap that tile with my bare hands.

 

So a relatively fragile, porous vessel, might be a good option.  It won't take much shifting around, underwater, to break it down.

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Recently I was looking for biodegradable bags online and read that some states have requirements for what can be sold as a biodegradable product. I think California was mentioned, and there may be others. There is apparently a difference between something bio degrading and it falling apart easily. You also don't want to create a product where the urn degrades but the finish does not, basically leaving Grandma's cremains in a plastic bag.

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Diane, that's why I like Bob's idea, of using a soluble coating, that when dry, would be fairly strong, but dissolve when wet.

 

Standard "Elmer's" glue would fit this criteria as well, very strong when dry, turns to much when wet.

 

And the vessel could even be decorated with tempera paint, which would also wash away.

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I agree with Diane that you'd better find out what you can legally call biodegradable.

Also, I think a thick walled urn made with about 40% paper fibers added would be quite strong as green ware. The extra weight of the walls would give ithe urn a certain presence as well.

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