It’s tempting to save a week-old slurry and run it again. The short answer is no: for predictable results, start every step, and every repeat of a step, with fresh grit. Here’s why, and what to do with the gray mud you pour out at the end of the week.
What happens to grit in the barrel
Silicon carbide is harder than almost any stone you will tumble. As it works, its grains fracture into smaller and smaller pieces. That is a good thing during the week, because each break makes a fresh, sharp edge. But after about seven days, coarse 60/90 grit has broken down into much finer particles mixed with rock powder.
- It cuts much more slowly: a second week on old grit does far less than a week on fresh grit.
- It’s no longer graded: you don’t know what size the particles are, so you can’t count on the result.
- It’s mixed with rock mud: that thickens the slurry and cushions the stones from the grit.
- It can contaminate the next step: leftover coarse grains are the top cause of haze in the polish.
Fresh grit costs very little compared with the weeks you put into a batch. See how much grit to use to measure the right amount for your barrel.
Never pour slurry down the drain
Tumbler slurry is a mix of grit, rock powder and water. In pipes it settles out and packs down hard, a lot like concrete. That goes for sinks, tubs, toilets and septic systems.
How to dispose of slurry safely
- Pour the barrel contents through a colander into a bucket, and rinse the stones over the same bucket.
- Let the bucket sit until the solids settle to the bottom.
- Pour off the clear water outside, onto gravel or soil, away from storm drains and streams.
- Let the remaining sludge dry out, then throw it away with your household trash.
Keep a dedicated “dirty” bucket for this and you’ll never be tempted to rinse in the sink.
Keep your steps clean
While you are emptying the barrel, scrub the barrel and lid with an old toothbrush and check the stones for cracks. Clean steps are the easiest way to get a glassy finish. Read the four-step rotary guide for the full routine, or stock up on fresh silicon carbide grit.