Why Bother Recycling Your Clay Scraps?

Every potter ends up with a bucket of bone-dry trimmings, cracked test tiles, failed handles and the odd collapsed cylinder. Tempting as it is to bin the lot, that material represents both money and energy. Clay is heavy to buy, heavy to transport and heavy to dispose of. Turning scraps back into usable clay saves cash, keeps your bin light and gives you a body whose habits you already know. If you work with a single clay body, recycling is straightforward. If you work with two, keep them apart — a sprinkle of stoneware in a porcelain bucket will show up in the glaze firing and nowhere else.

Sorting Before You Soak

The cardinal rule of recycling is keeping your scrap clean. Just a few grams of plaster, whether from a mould or a bat, will cause lime pops that blow out of the finished pot weeks after firing. Set aside any clay that has touched plaster and bin it without hesitation.

• Keep one bucket per clay body, clearly labelled with the name and supplier.
• Scrape off glaze, slip decoration and sandpaper dust before anything goes in.
• Shake out the crumbs from your splash pan and floor — grit is the enemy of a smooth body.
• Keep leather-hard scraps separate if you intend to rewedge them directly without slaking.

The Slaking Bucket

Slaking is simply letting water do the hard work. Fill a plastic bucket roughly two-thirds with dry scraps, then pour in water until it just covers the clay. More water means a longer drying time later, so resist the urge to flood it.

Leave it overnight, or a full twenty-four hours if the scraps are large and hard. The clay will slump into a sludgy mass, usually with a dry crust floating on top. Push that crust under with a stick or a stiff whisk and leave it a few more hours. You want a consistency somewhere between thick cream and yoghurt, with no dry lumps hiding at the bottom of the bucket.

Mixing, Sieving and Checking Consistency

Now break up whatever is left. A hand whisk works for small batches; a drill with a mixing paddle, run slowly, is quicker for a full bucket. Aim to eliminate lumps rather than to whip air into the slip — trapped air causes pinholing and short-term weakness in the body.

For a really clean result, pour the slip through a sieve. An 80-mesh sieve, around 180 microns, catches hard crumbs, dried glaze specks and stray plaster. Push the residue through with a rubber kidney, or discard it. Your reclaimed clay will feel noticeably smoother afterwards, though you lose a small percentage of coarse material.

Test the slip by dipping a finger: if it coats evenly and drips slowly, you are close. Too thin and it will be sloppy to handle; too thick and the particles will not settle evenly.

Drying to a Workable State

This is the stage most people rush, and it is the stage that decides whether your reclaimed clay behaves. There are three reliable approaches.

• Plaster bats: spread the slip over a plaster slab or biscuit-fired bat and leave it. The plaster draws water out quickly, so turn the clay every few hours for even drying.
• Cloth and board: spoon the slip onto a cotton sheet laid over a board. The open weave lets water drain, and the clay lifts off cleanly once firm.
• Bucket and air: leave the slip in an open bucket, stirring daily, until it stiffens enough to handle.

Whichever method you choose, stop while the clay is still slightly softer than you would like. It firms up as it stands, and you can always add a splash of water — but you cannot easily take it out. Aim for the same softness as fresh clay from the bag.

Wedging and Testing

Reclaimed clay is rarely uniform. Water has migrated unevenly, particles have separated, and pockets of softness sit beside pockets of stiffness. Wedging solves this.

Use the ram's head method for a thorough mix, or spiral wedging if you have the space. Work in batches small enough to handle comfortably — a two-kilo lump is plenty. Fold, press and repeat until the whole mass feels consistent and there are no soft spots under your thumbs.

Before committing reclaimed clay to a good pot, make a test piece. Throw a small cylinder and check how it forms, how it takes a handle and how it fires. Reclaimed clay can be slightly shorter than new clay because the fine particles have been separated and recombined, so it may need a little more care on the wheel. It is often happiest in slab work, press moulding or sculpture, though plenty of potters throw with it quite happily.

Storing So It Keeps

Once wedged, shape the clay into a ball or a squared-off block and wrap it tightly in a plastic bag, pressing out as much air as you can. Double-bagging is worth the trouble. Store somewhere cool and dark, away from frost and radiators.

Label the bag with the clay body and the date. Reclaimed clay can sit for months, but mould will eventually form on the surface — harmless, easy to wedge back in, though it smells distinctly earthy. If you are keeping it a while, add a damp cloth inside the bag and check every few weeks. Airtight buckets suit larger amounts particularly well.

One final caution: never tip reclaimed clay into a fresh batch without checking it first. A small test piece tells you more than any amount of squashing and squeezing, and it takes only a few minutes. Recycle regularly, keep the buckets labelled, and your scrap heap quietly becomes one of your most useful supplies.