Originally Posted by trugger
I let it soak in a while, then press it.
I have a white residue after pressing.
The white residue is starch sitting on top of the fabric; it hasn't soaked in.
If you haven't pre-washed your fabrics, they likely contain finish coatings from the factory that may retard absorption of the starch. I don't pre-wash my fabrics, and this is one of the reasons why I think spray starching doesn't work well for me. I have even scorched the starch!
If you want to continue spray starching, you may need to spray the entire yardage and roll it up for awhile to allow the starch to be absorbed. Alternatively, you could pre-wash your fabrics before spray starching.
If the fabrics have been pre-washed and you are having this problem, I will be interested to hear other explanations of what is happening! When you say you let the starch soak in for awhile, how long is awhile?
If you are starching yardage, you may want to switch to my method of "painting" on the starch solution and then drying in the dryer before ironing. In this case, I am saturating the fabric with water and starch and rolling it up to allow absorpotion before drying. For piecing, I would use more like a 1:2 or 1:3 starch solution (water:starch) for this. I use a 1:1 solution for starching fabrics that are going to be used for machine applique backgrounds and/or for cutting bias strips for binding.