Varnish - Water or Oil Based?

There are two disadvantages to using water based varnishes:

1. When the first coat is applied to bare wood, it will “raise the grain” and you will need to sand it smooth for subsequent coats. This should be done with any varnish of course, but it's more noticeable with water based finishes.
    
2. It is a bit thinner, so you may have to do an extra coat.

One more point – depending how you look at it, either an advantage or disadvantage. Water based varnishes do not yellow over time, so your wood will retain its original appearance for years to come. However, it will never get that aged patina that makes some old woodwork so beautiful.

How to apply varnish.

Whether you use water or oil based varnish, it is imperative that you use a very good brush. The end result will be smoother and the job will go faster.

Sand between coats, using fine sandpaper or sanding pad.

Tip: Used dryer sheets make fantastic dust cloths for cleaning all the sanding dust in between coats.
Note that acrylic varnishes tend to go on slightly "milky" looking but dry clear. Don't freak out when you see this!

Can you put water based varnish over oil based varnish?

This depends. No matter what, you will have to very thoroughly sand the original surface (using fine grit sandpaper) to ensure a good bond. If the area is very high-traffic – like flooring or kitchen cabinets – I would be tempted to stick with a good oil based varnish for better durability.

Can you put oil based varnish over water based varnish?

Usually, yes, if the underlying surface is in pretty good shape and you sand it well.

In both cases, read the manufacturer's label. There are so many different clear coatings on the market now (and I haven't even mentioned lacquer here) that you need to check for compatibility.

Speaking of lacquer finishes.

Most newer homes with wood stained and finished trim are lacquered instead of varnished. It is generally fine to put either a water or oil based varnish over lacquer as long as you sand first. You cannot put lacquer (either spray or brush type like Deft) over any other finish, though. It will usually lift and bubble up the underlying coating and then you have a BIG mess on your hands!

So – for general household applications, I think water based varnishes are the way to go. I have had very good luck with it over the years.

-Carina MacDonald

Carina MacDonald has been a painting contractor since
1979 and has tackled everything from large commercial buildings and Victorian homes to faux painting a child s room and wallpapering a bathroom. If it stands still long enough, she can figure out a way to paint it correctly!