I consulted with an award winning machine quilter, and she had already tested the pens. She ironed them away, stuck the fabric in the fridge, and the marks came back. Re-ironed the marks away, stuck the fabric in the fridge, and the marks still came back. She also tried washing out the marks, but they still keep coming back. Now if you live in the heat of the desert, the marks are less likely to come back than if you live in Minnesota or even up here in Lake Tahoe where 14 degrees is not uncommon in the winter.
Keep in mind that these pens were not originally designed to use on fabric. They are great fun to use on paper. Something else to consider is what the marks may do to your quilt over time. Remember, we make our quilts to last a long time. So if the marks are really still there, just "turn clear", is that really what you want on your heirloom quilt?
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