once the item is washed the marks are gone....but till then you can iron and then freeze then iron etc. many times.
we stopped 'testing' at 25 times on a fat quarter...then washed it and it marks did not re-appear when frozen....do not know if chemical is actually truly gone or just not visible.....

as for the students who buy used but unmarked textbooks and then put them in the freezer...hope the previous owner was an 'A' student......

In middle school the blank piece of paper that is passed in class...becomes a note when wrapped around a cold juice or soda can at recess.........tech savy kids today

You gotta love that "creativity" of those middle school kids!!! This gives me something to watch out for next school year!! LOL!!!

I love my Frixion pens. I use them often to mark myFMQ lines. So far they have worked well. I have not used them much on darks. Yesterday I was machine embroidering a shirt for my dad. I marked a box on a medium blue t-shirt to keep my embroidery straight. I used a black Frixion pen. When I ironed it out it left a light line. I had an OMG I ruined it moment. I washed the shirt and the line is gone. I will have to make sure I test it on my fabrics in the future before making a whole quilt

i have tested it on dark fabrics - got the white line, so i use something else on dark fabrics. You took it one step further by washing it, i did not do that - will have to try that. I also love my frixion pens for marking my quilts!

I love the Frixion pens as well and now they have them Highlighters too. I love this idea as I can use them on my patterns without leaving a permanent mark on them. I just high light the area I need then remove it..... :-)

Oh and an FYI you can get them at Staples if you happen to have them in your area...also Amazon.com

I have read that if you use them on fabric that has been treated with starch the lines will fade in the wash but not come out completely. I use the pen carefully.

I've used them quite a bit and have had no problem. None of my quilts have gone to extreme cold so I'm not worried yet.

I used a red one quite some time ago on dark fabric and it left behind a white line. Now I only use them to draw on back of fabric.

Seems like when I bought mine, the girl said a hot iron will remove the seam and a little water will bring the line back. She also said the quilt or item would need to be washed with soap to remove all the ink for good.

Just used my frixion pilot pink FX7 on black, guess what, I now have a permanent white line. Tried everything and now I am ripping put and replacing the strips.