Enzyme desizing, explained for production managers

Why size is there in the first place

Warp yarns are coated before weaving so they can take the abrasion of the loom. Starch is the classic size on cotton: cheap, effective, and completely in the way afterwards. Left on the fabric it blocks the scouring and bleaching that follow, and it blocks dye uptake — which is why a desizing problem usually shows up as a dyeing problem two stages later, and gets blamed there.

So the first question is not "which desizing chemistry" but "how much size is on this fabric, and did it come off". Everything below follows from that.

What the enzyme does that an oxidative route does not

An amylase hydrolyses the glycosidic bonds in starch. It does that and essentially nothing else: it has no useful reaction with cellulose, so the fibre is not part of the target.

Oxidative desizing is not selective in the same way. It will remove the size, and under the wrong conditions it will also attack the cotton — which shows up as tensile strength loss, and shows up too late to do anything about. That selectivity is the whole argument for the enzymatic route, and it is a stronger argument on a high-value or fine-count fabric than on a heavy drill.

The second argument is the effluent. An enzyme is a protein: it works at mild conditions and it degrades. It does not add an oxidative load to a wastewater plant that is already being asked to do more than it was designed for.

Where it sits in the sequence

Desizing is the first wet stage. It comes before scouring and bleaching and long before dyeing, and every stage downstream inherits whatever it leaves behind.

Two practical consequences. First, an enzyme is only as good as the wash-off that follows it: the amylase cuts the starch into soluble fragments, but something still has to rinse those fragments out of the cloth. A plant that switches chemistry and keeps a marginal wash box has not solved its problem, it has moved it. Second, anything that deactivates the enzyme before it has finished — a carry-over of the wrong chemistry, a bath that is far outside the enzyme's working window — produces a partial desize that looks fine until the dyehouse sees it.

What to measure in the first week

Do not judge a switch by how the fabric feels.

• Residual starch. The iodine test is qualitative, quick, and enough to tell you whether the size is gone. Run it on the same positions on the fabric, every batch, for the first week. This is the measurement that actually answers the question.
• Tensile strength. The reason for switching, on many fabrics, is to stop losing it. Take a baseline before you change anything, or you will have no way to demonstrate the gain.
• Dye uptake and levelness on the first dyed lots. Desizing problems surface here. If levelness improves, that is the switch paying for itself.
• What the wash boxes are carrying. More soluble starch fragments in the wash water is the enzyme working, not a fault — but your effluent plant should be told before it sees the load, not after.
• Bath conditions, logged. Every enzyme has a window it works in. Whether your line is holding that window is a fact about your equipment, and it is the first thing to check when a batch comes out short.

What we will not put in an article

Temperatures, pH ranges, dose rates and hold times belong on the technical data sheet for the specific product, against the specific fabric and the specific water. Published as general advice they are worse than useless: a number that is right for one amylase on one line is wrong on the next, and the reader has no way to know which they have.

Tell us the fabric, the size, the equipment and the water, and we will give you the conditions for the enzyme we would actually put on your line — and trial it there before you commit.