This section is from the book "Clothing For Women: Selection, Design, Construction", by Laura I. Baldt. Also available from Amazon: Clothing For Women: Selection, Design, Construction.
When the trial pattern has been corrected, practice taking each other's measures; after these have been verified, draft pattern of shirtwaist and sleeve to your own measures. Test for accuracy of measurement. This pattern should then be cut in inexpensive cambric or muslin, fitted, and alterations made, and pattern corrected before cutting into material for waist.
It is best to test all skirt, shirtwaist and sleeve patterns, in inexpensive materials, before making up. Light weight unbleached cotton cloth or cambric is suitable for this purpose. It is well to have a goodly supply of such material, if one is doing a great deal of sewing. Keep muslin skirt patterns; they can be used for testing smaller garments, waists, sleeves, collars, etc. When alterations are made in these patterns, they should be made also on the original paper pattern, and the latter used in cutting the garment, as otherwise there is likelihood of the neck and armhole lines being stretched; the edges of the paper pattern are also firmer for marking seams, which is at least safer, for inexperienced workers.