There are a lot of various problems with different markers. I prefer using white powdered chalk except that doesn't work on light fabric. Beware NOT to use any of the powdered chalk that is blue, yellow and red. They will NOT wash off.

Of course the maker isn't going to say it's made to use on fabric when it's not marketed for fabric. Doesn't change my mind about using them.

A friend of mine used them to mark a show quilt. She had washed the quilt to block it and the marks reappeared. Nothing she tried got them out. I prefer to use a product specifically manufactured for marking on fabric or something that will easily brush or wash out like chalk or a sliver of soap for dark fabrics. I use blue water soluble markers for light but only after testing.

I was under the impression after they are washed the lines do not come back.

This is exactly where I stand also. FriXion pens, no matter what the manufacturer says NOW, were not originally developed for marking on fabrics.

I have used these pens I like them , but then I live in a warm climate so it wont be something I will need to worry about .

I use either just a plain old #2 mechanical pencil for light fabrics and the Bohin mechanical pencil in white for dark fabrics. Only one time did I have an issue with the #2 pencil on a very white fabric but did manage to get that graphite out. Personally, I would not use any ink-based product for marking but that's just me.

there is product out there that remove the lines permanently. I have also steamed and did a wash test and did not have lines appear but the quilt had to be washed, so they can be used you just have to keep this in mind

I use Frixon pens all the time in my sewing room for writing notes and some marking because I know if I accidentally get some marks on the fabric or clothes they will wash out. I am cautious about using them to mark a quilt for quilting because I have had them leave shadows on fabric - especially the red one and red fabric - when you iron them away. I use a chalk pen for darker fabrics and either a blue water soluble or purple air soluble for marking for quilting. I wash all my quilts after they are done anyway so whatever is there is gone after the wash.

I only use the Frixon pens to mark embroidery lines. When ironed away, if they come back, they are under the thread. Will use them until they are dried up, but will not buy more.