Determine if Coating on Floor is Shellac or Old Polyurethane?

[bro]

I removed the wall to wall carpet from the 70 year old house I recently bought. The floors in the bedrooms appears to be pine coated with shellac or possibly polyurethane. I don't want to refinish the floors because of the beautiful patina. In only isolated spots and by the door the coating show heavy wear.

How can I find out which coating is on the floors? How can I protect and preserve the floors? What should I use to clean and preserve them?

Thanks,

Mike

[Don Young]

Shellac will completely dissolve in alcohol. I do not know how to identify polyurethane. Don Young

[bro]

I'll try some denatured alcohol.

Mike

[nospambob]

[bro]

90% of the floor looks good and I really don't want to refinish them. If it's poly coated I can sand (which grit sandpaper?) then recoat with poly? Dpes it matter if it's water based poly?

Mike

[bro]

How do I know if I need to fresh coat to be oil base dor water based? Does it matter?

Mike

[nospambob]

[bro]

Do I need to find out if the original poly is water based or oil based before applying a top coat?

Mike

[J Kelly]

No, you can apply water over oil. Whether it is oil or water you are covering over you will need to lightly sand. I doubt a 70 yr old floor is poly though. Poly wasn't invented until the mid 50's. What did you find with the alcohol test?

[bro]

The house went through a major renovations during the 70s and 80s. It appears the floors have been refinished (power sanded) at once. Haven't tried the alcoholl yet. Going to test this weekend.

Mike