If it is just stain and you are going as dark or darker you can. If you are going much lighter or it has a protective coating on it then it should be stripped with a paint and varnish remover before sanding.Can I re sand hemlock to change a stain I previously used
You can use a stripper, and then sand, and you may not get all the stain out. It would depend on how much penetration there was.Can I re sand hemlock to change a stain I previously used