I use a travel iron that i only use for this and nothing else. If you don't want to risk messing up your embroidery work, I would put a piece of cotton fabric between your work and the iron. You can also use a blow dryer to erase the lines. (if you used Frixion heat erasable pens)

If you used anything else to put your pattern on the fabric please see the instructions on how to erase visible lines.
When I use a Bohin transfer pen which I only use on dark fabric I try to cover all the lines because these lines are not so easy to make disappear after stitching.

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