I have tested that new pen. I was told that freezing will make the marks re-appear, and it does!!! I marked several pieces of cotton fabric. The lines show up great.
I ironed the fabrics, the marks became invisible. I washed the fabrics to get the marks out, then put the fabrics in the freezer for a couple of hours and the marks were all back....very visible!
That means to me that the chemicals are still in the fabrics, and you don't want to use quilts in a cold environment! WHAT???
I won't use these pens on my quilts. There is no telling what the chemicals will do to the fabric several years from now.
However it would be a fun project for children to send secret notes to each other!!

Thanks for the heads up Margo, it is always good to hear from the practical side of things with new 'toys'. By the way was it just one wash or multiple washes? Any chance that when you are doing a load, you could throw your sample in and see how many washes it takes to remove the ink/chemicals and report back for us? (grovel-grovel