You CAN iron velvet but it requires a towel. A fluffy cotton towel, not a presscloth.
Put the towel on your ironing surface, and then lay the velvet on top of the towel with the nap side DOWN so that it's against the towel. Iron on the wrong side.
The towel's fluff creates a space buffer and prevents the velvet nap from being crushed by the weight of the iron. Never iron velvet with the iron surface against the pile. Unless it's just a seam allowance, in which case that doesn't matter because it's not visible from the outside.
If you're paranoid about having the right temperature setting or whether you're using a proper type of towel, test on a scrap first.
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