We have tried: We lightly drew fine lines on the interlining with chalk in a pencil (070209, 050769). After soaking / washing the embroidery, the chalk disappeared. We also tried the textile marker, which you can find under the code 020975 - it slightly melted on the interlining and left a strong trace of the drawing. It is always a good idea to first test how the chalk draws / writes on the rest of the material to avoid damaging the embroidery.