I had remembered that Geta Grama had done a quilt with very thick thread so I started there.
One of her posts talked about how supplies can be hard for her to get or at a much higher price. In a moment of genius she tried washable markers!
So here I am to show you my own discovery of washable markers.
I grabbed 3 fabrics and a marker. The bottom fabric is so dense in design it is hard to see anything. But I did do white, so there is that.
The three lines in the left have no extra treatment, the ones in the right are steam ironed.
Washed by hand with cold water.
Allowed to air dry.
While I wouldn't recommend ironing, the marks did come out. I had to rub the ironed side at all where as the regular side dribbled down the drain quite quickly.