How Much Size to Put on a Warp

How to read this sheet

Read the three department columns across, not down. Every row that says to add size is a row where sizing and the effluent plant both spend more and the mill is better off, and every one of those changes has to survive a conversation with somebody whose budget it comes out of. That is the actual obstacle to this decision in every mill that has ever taken it, and the sheet exists to put a number on the other side of the conversation. A mill that asks its sizing department to reduce size consumption will get exactly that, and will pay for it several times over in a shed it is not looking at. The rule to keep. Warp kilograms a year, times one per cent, times the cost of the size plus the cost of washing it off, divided by what a break costs. That is how many breaks a year one point of add-on must remove before it pays for itself, and it can be worked out at the sizing machine on the back of the recipe card. It is far smaller for a quality with little tonnage than for a big running quality, which is why the same add-on policy across a range is wrong even when the yarns are similar. Why only three points. Three levels the mill has actually run are enough to find a turning point and are not enough to draw a curve, so the answer is held to a short distance either side of them and the sheet reports every quality where it has been held there. If a quality is being held at the edge, the answer is not to trust the extrapolation - it is to run a trial at the level the sheet is pointing at and put the result in as the new middle. Where the curve does not turn upward at all, the three points say the add-on is somewhere on a slope rather than near a bottom, and the sheet declines rather than extrapolating off the end of what is known. What is not modelled. Size is treated as one material with one price, where the mix of starch, PVA and acrylate changes both the cost and the break curve, and a mill that changes the recipe rather than the quantity is outside this sheet. Nothing here values the fabric: an over-sized warp can weave beautifully and finish badly, and size that will not wash out cleanly is a wet processing problem that costs more than either the starch or the breaks. Loom stoppages are counted at one cost, where a break in a fine shirting on a fast air-jet is not the same event as one on a heavy rapier. And the effluent cost is charged per kilogram of size, which is right for load and wrong for a plant that is already at its consent limit - there, the cost of another kilogram is not a chemical bill, it is the whole plant.