Do I need to change the reduction-clearing recipe for different dyeing machines?

Direct answer

The same reduction-clearing recipe often behaves differently on different machines, and the difference comes down to three things: liquor ratio, mechanical action and how the liquor circulates. Thiourea dioxide is dosed in small amounts and is sensitive to temperature, so all three matter more than they do with hydrosulfite.

1. How four machine types differ

2. The key conversion is dose per kilogram of fabric

When the liquor ratio changes, dose by fabric weight, not by bath volume:

• Recipes are often written in g/L, where g/L x liquor ratio = grams per kilogram of fabric
• Convert to g/kg first, then recalculate the g/L for the new machine and confirm on a bench trial

Example: 1 g/L at a 10:1 liquor ratio is 10 g/kg; on a jigger at 4:1 that corresponds to about 2.5 g/L. That is only the conversion, not permission to run 2.5 g/L: mass transfer is faster at a small liquor ratio, so the actual dose is usually lower than the converted figure.

3. Four operating points

1. Convert, then trial: work in g/kg, then confirm on the actual machine

2. Establish the heating rate separately: airflow and jet machines have different curves

3. Top up by carry-over: the water and chemical the fabric takes out is what determines the top-up

4. Record the machine: keep a separate record for each machine running the same recipe

4. Common misconceptions

• Treating g/L as a universal recipe: change the liquor ratio and the actual dose changes with it
• Scaling up directly for a small liquor ratio: mass transfer improves, so less is usually needed
• Sharing one process card across machines: at minimum, heating and circulation parameters must be separate

Sources

Liquor ratios and the conversion method are standard textile practice; the temperature and alkali conditions for thiourea dioxide come from our technical data sheet and must be confirmed on your own machines.