Clay and Material Waste: Recycling Scraps and Calculating True Material Cost
You trim 200g off a pot to fit the kiln shelf. You have 15% scrap from wire cuts. Without recycling these scraps, your actual material cost is 15-20% higher than the finished piece weight. This guide teaches you to recycle clay and calculate true costs.
Where Clay Waste Occurs
Wheel throwing: Centering waste (5-10% of ball), trimming (10-15%), sponging (1-2%)
Hand-building: Cutting/assembly waste (5-15%), joining overlap (2-5%)
Wir cutting/slicing: Tool width loss (1-3% per cut), test pieces
Drying/firing: Cracked pieces you discard (2-5% if you don't fire them)
Total typical waste: 15-30% of starting clay weight. If you're not recycling this, you're losing money.
Recycling Clay: The Simple Method
Most small potters use the slurry method:
Step 1: Collect All Clay Scraps
Trim, wheel waste, hand-building scraps, broken greenware (unfired pieces). Store in a bucket.
Step 2: Slake the Clay
Dry the scraps (2-3 weeks). Break into small pieces. Add water until it becomes a muddy slurry. Stir occasionally (5-7 days).
Step 3: Allow to Settle and Dry
Let slurry sit in bucket for 1-2 weeks. Water evaporates/drains. Scoop clay back to working consistency.
Step 4: Mix Back Into Production Clay
Wedge recycled clay with fresh clay (50/50 ratio). Use for new projects.
Time cost: 30-45 minutes per month of active collection. Labor savings: enormous (recover 15-20% of material cost).
Calculating True Material Cost With Waste
Example: Ceramic Mug
Finished mug weight: 400g
Typical waste rate (throw + trim): 20%
Starting clay needed: 400g ÷ 0.80 = 500g
Clay cost @ $0.30/lb: 500g = 1.1 lbs × $0.30 = $0.33/mug
Without recycling, true material cost is $0.33 per mug, not $0.24 (what 400g would suggest)
If You Recycle 80% of Scraps
Scrap collected: 100g per mug
Recycled back: 80g (80% recovery)
Net fresh clay needed: 500g - 80g = 420g
New material cost: 420g = 0.93 lbs × $0.30 = $0.28/mug
Recycling saves $0.05 per mug (15% material savings)
At 100 mugs/month, recycling saves 500g/month of clay = $1.50/month or $18/year. Scale to production volume.
Key Takeaways
✓ Account for 15-30% clay waste in your material cost calculations
✓ Recycling clay through slurry method recovers 75-85% of waste clay
✓ Recycled clay reduces material costs by 10-15%
✓ Slurry recycling requires minimal time (30 min/month) for significant savings
✓ Include waste factor in pricing: Material Cost = Finished Weight ÷ (1 - Waste %)
Recycle Smart. Reduce Costs.
TrueCraft tracks material waste and recycling efficiency.
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