Navigate / search

Natural Clay Pottery Course, 2020

Welcome! The Museum of Ontario Archaeology, in partnership with FUSION: The Ontario Clay and Glass Association and The London Potters’ Guild, is excited to offer a new socially distanced take on our Natural Clay Pottery Course.

All course materials can be accessed on this webpage. The numbers below indicate each session where content will be continually uploaded during the course.

Content will remain available during and after each scheduled session for the remainder of the course. Session 1 begins on the next sub-page.

FAQ and submitted questions are on page “9” below. We will continually update this page throughout the course!


Heather E. Hatch

Hi folks,

I had a chance to go grab some clay yesterday, and lucked into one of those really pure deposits that Kim was talking about (I’ll try and post some pictures on the references page – if anyone else wants to send in pictures we would really appreciate it!).

I had a few observations – it was actually really easy today to break apart the chunks I had by hand, so I went ahead and did that, and though I would try screening them at that stage, while the clay was still damp. It worked really well! I would say this is worth trying if you get clay from the bottom of a stream or river that is still damp.

I watched the reference video that Gene provided and thought I would try the dry process with the clay form some of those bigger chunks, but I now have a question for our instructors:

I have the dry clay, but I know that the Ontario clay we get from the area around the museum has a lot of limestone that needs to be dissolved. Do you think it would work to try mixing the dry tempered clay with a vinegar/water mix? Or should I add temper then slurry it, add vinegar to dissolve everything, and temper, and then dry it like I would with regular wet processing? I don’t have enough to try both this year. Thanks!


Hi Heather,
Vinegar is mostly water so use it to wet your clay. The acid will react with the limestone to remove it. A slightly acidic clay will be fine to work with.

Kara Bunn

Should we stick to one source for our clay or can clay from different areas be mixed? With purchased clay you can if you know the cone the clay fires to buy I wonder if it is the same for pit firing?


Hi Kara,
Commercially prepared clay is a blend of different clays with known properties blended together to achieve a certain goal. I don’t see a problem with mixing clay from different sources as long as they are blended from the start in dry form.

Richard Zane Smith

greetings! as a full time ceramic artist processing natural clay for 40 yrs, I find the best way, is to let time and water do most of the work.We might not have enough time to do this for this class but i hope anyone who wants to continue making pots form hand dug clay will keep this in mind. Dry ones dug clay in the sun on a large 4×8 sheet of plywood supported by cinder blocks. Once its completely dry, it can be crumbled into water, and left for several hours, no stirring. After a few hours one can reach down in it and feel if there are still chunks. if so its left longer. Once water-saturated its whipped with a long flexible stick (or use a drill with a paint mixer attachment) Add water to this mixture till its like thin cream. Skim off organics and pour the fine slurry through a screen into another bucket. A window screen can be cut and tied around a 5 gal. bucket. I use an 80 mesh screen. Water will chase the clay through and with just a bit of light brushing the finest clay will pass through. Organic material and stones are discarded. the bucket of sieved clay is now ready to sit aside and settle.Water is periodically siphoned off over a couple weeks. when there is no longer water to siphon off. this is the time to add temper. 40 lbs of settled clay slip, (no water on top) will take 15 lbs of dry temper. this is stirred in. The clay (in a thick milkshake stage) can be stored indefinitely under a fitted lid.. I always mix enough for a year at a time. a week before i want clay for making pots, I’ll scoop out this thick slip and spread it like thick frosting on a cloth covered slab of plaster about an inch thick. it is ready to be wedged in about 2 days. Its aged, and ready to be used. About vinegar. I’m no pro with it, but i find its more effective to dissolve limestone or gypsum crystals AFTER firing. Many of the Acoma potters in NM will give their freshly fired pots a vinegar bath. it dissolves any gypsum before it gets a chance to swell and pop. Just some thoughts!

Lynn Nelles

I have a question about temper, would this be suitable?
Fine Stone Granules By Ashland™ Its crushed quartz sold at Michaels

Richard Zane Smith

Lynn Nelles,
I think that’s a great question. I looked up the product online, and since it is used for fish tank gravel under water, it should be fine mixed into clay. Its worth an experiment. I’m not sure of the particle size, but if it passes through a window screen it should be ok. it might be a bit coarse, and make any burnishing more difficult, unless you could grind it down further. but you might be on to something as far as locating a possible temper from a non-ceramic environment.

Leave a comment


email* (not published)


This site uses Akismet to reduce spam. Learn how your comment data is processed.