Q: I had problems with the third coat of poly drying too fast and leaving lots of bubbles. So, I hand sanded with 100 grit, and with the 4th coat decided to cut the fast dry poly with 25% mineral spirits to ensure no bubbles, and let it slow dry (no ventilation). Now I can see all the sanding marks on the floor?
Did cutting the poly cause this?
A: 100 grit is far too rough to buff polyurethane. If you have access to a polisher, knock it down with 180-220 grit. I would almost bet you are using M****** polyurethane. If you want to use an amazing finish, contact poloplaz.com and have him send you a gallon or 2 of Primero in whatever sheen you need. Note: Satin will tend to hide the sanding and other marks much better than gloss.
Follow-up Q: Thanks for the suggestion. You’re right on the M*****. The Big brand out there obviously. I must be prone to leaving bubbles. Unfortunately, I had to put my house back and will let the floor “wear inâ€. I learned tons on this project. From all the mistakes I learned from, I will be a pro refinisher on my next project. Great website, thanks.
A: M***** is a “big brand” for the home DIY person. Few if any professionals would use the stuff. You should do better next time around. I have to warn you though. This trade is so difficult and involved, it really requires an apprenticeship over a period of time to even become qualified enough to be left alone on a job. Good luck.