Choosing a batch size

Unusually flexible compared with the other crafts in this estate, because nothing is setting or curing while you work.

What sets the ceiling

Vessel capacity and whether you can mix the whole volume properly. An under-mixed batch is not one batch; it is a gradient.

Your ability to move it. Water weighs a kilogram a liter, and a 50 liter batch is 50 kilograms in a vessel you may need to lift or tip.

And how long the product can sit before filling, which for most water-based cleaners is comfortable.

What sets the floor

Weighing accuracy for minor ingredients. A preservative at 0.5 percent of a 2 kg batch is 10 g, fine; a dye at 0.01 percent is 0.2 g, which needs a better scale.

And pH adjustment, which is hard to do precisely in a small volume because a single drop moves it a long way.

A practical number

Ten to twenty liters for a hand operation: enough to weigh everything accurately and to fill a meaningful number of bottles, and light enough to handle.

Scale by running more batches rather than bigger ones until mixing equipment changes what is possible.

Keep the batch a whole number of fills where you can, so there is no awkward remainder sitting in a drum.

Batch size and testing

Development batches should be large enough to be representative: a one-liter trial can behave differently from a twenty-liter one, particularly for anything thickened or emulsified.

And retain samples from every batch, which is a cost in bottles and is what lets you answer a question about a batch a year later.

Two retained bottles per batch, labeled with the batch number, stored where you can see them.

References