Alkyd or latex? How do you tell?

Just bought a house and can’t find any paint cans in the basement to tell me what the previous people painted the walls. Is there a way to tell latex from oil? I want to paint with latex but know there can be problems if you paint it over oil. Any tips?

latex is usually softer than old alkyd or oil paint. Find a portion where the paint is thick and see how hard it is. Old alkyd will be hard and brittle.

There is probably a fool proof way. there should be a painter around on this board that could help

(as an ex-paint chemist I would always run a spectroscopic analysis on any sample sent to me for analysis but that is little help to you)

How old is the house interior? and how old does the paint job look? Usually interior paint is latex. Within the past several years even so-called alkyd paints are also latex. Consider putting a primer down (I almost always do this nowadays to ensure better coverage pricey paint) and then it is a moot point.

Take some rubbing alcohol on a cotton ball. Rub the wall with it. If paint comes off onto your cotton ball, it’s an OIL BASED paint. If that’s the case, you need a special primer (ask at the paint store). Otherwise, your latex paint will LOOK great when you apply it, but will start chipping off very soon after.

If it’s latex (which nowadays is also alkyd), then the base is water. You’ll have no problem painting over it. However, there are a few things to consider. If it looks like it hasn’t been painted in a while, your walls are “thirsty” ~ they’re going to need extra paint, in which case, a primer would be a good idea. Also, if it’s a darker colour and you prefer something much lighter, primer would also cut down on your work.

Don’t skimp on the rollers you buy. The tools are what makes the job. $1-store rollers look like a great save, but you end up with their lint all over your walls. You can get some that promise the job done in one coat. Though this is rarely the fact (and their guarantee is under specific circumstances), you’ll have a much nicer time with this job.

Good luck and happy painting :stuck_out_tongue: