Stripping Paint : Understanding your paint

Jun 20th
Stripping paint again

Stripping paint?  Me?

If you have an old house, then you have old paint. Were you lucky to buy from someone who was meticulous and stripped it all for you?  I envy you.  Ever since I was a kid, I’ve lived in old houses, and stripped paint.  You have an old house?  You have to strip paint.

Paint is all over:  inside on your woodwork and walls and moldings (which may not be wood).  Outside on your siding and shingles.  Even on your ceilings and floors and stone and brick.  Chances are that short of your windows, everything has been painted at some time.  At some point, to make your house look good again, you or someone you pay will be stripping paint.

There is a lot to know about stripping paint, and from having stripped for hundreds of hours, I have a few things to say about this fascinating subject.  Do I know all the tricks?  Heck no.  Do I like stripping paint?  Heck no.  Do I have the money to pay someone else who doesn’t know much about stripping paint and will do a half baked job?  Heck no (I did that twice already, which is why the third time around I am the charm).

So here I am, stripping paint on my 1903 transitional house (Edwardian to Craftsman), when I though that I would never have to strip again.  Why?  Because the guys that did the work the first time 10 years ago didn’t do it right.  And the guy who “fixed” it three years ago didn’t do it right.   And it took about that long for their mistakes to reveal themselves.  But I’m getting ahead of myself here.  Let’s just say that stripping paint again motivated me to write this all down for you.

Understanding your house’s paint

I like to understand what is happening when I put the paint on, and when I strip it off.   I’m going to start by helping you understand too.  You want to understand how to strip paint and do a good job and not get totally frustrated and have to redo it 10 years down the road (because you are really in love with your house and want to live there forever, right?, and pass it on to your kids?).  So that means you have to understand two things: paint and the surface its painted on.  Not just today’s paint, but paint that was around for the time your house has been around.  Before you even strip paint or buy any products, you need to understand your house’s paint and the surface below.  Why?  Because they all strip differently.

Types of paint in an old house

Think of your house’s paint as a reflection of the fashion of the times.  Every era had its own type of paint that it used, based on  chemicals available, and cost of production.  There’s not anything wrong with paint from 100 years ago. In fact there is a lot of good about it, but that is a whole ‘nother post.  Like fashion, paint  evolved to reflect the products and technology available, and hit a cost / convenience point in the market.  Let’s take a brief look at the three major types.

Latex Paint

From about the 1950s and on, Latex paint came into fashion.  You can use clothing as an analogy.   Synthetic fibres give you new fabrics that bend and shape to your body.   Synthetic polymers today give you  latex paint, so-called eco-friendly because it is low in VOCs (Volatile Organic Compounds).  It dries fast.  You clean it up with water. You get just about any color you want in any finish you want.  It goes on smooth and flows beautifully into cracks and crannies making minor imperfections in your prep job seem to disappear.   When latex paint has dried, you are basically left with a thin skin of plastic (synthetic latex or polyvinyl acetate) on your surface.

Oil based Paint

In the 1920s, even until today, you’ll find oil based paint on the surfaces in your house.   Oil base paint is a dream to work with if you need a long dry time.  Why would you want that?  Because long dry time gives more time for your paint to “flatten out” minimizing brush marks. It is becoming harder to find oil base paints for that very reason, because VOCs are used to help speed up the drying process.   Think about it, just how fast does oil dry?  If you have a house that is pre 1950s, there’s a pretty good chance that you have oil based paint.

And lets have just a little discussion on lead based paint.  Lead was used as a pigment and drying agent in paint until it was outlawed in the late 1970s.  So if you have a house that has oil based paint, play it safe and get a test kit to check for lead before you start stripping.

Oil based paint is much stronger than latex, it bonds better to itself and the subsurface ( in my opinion from taking the darn stuff off,  I’m not a paint expert here).  It also strips much differently than latex paint.

calcimine paint / Limewash

If you have a house built at the turn of the last century or older, chances are you are going to find some calcimine based paint on your interior plaster walls.  I’ve never found it on interior woodwork, but I’ve only worked on houses from 1890 on.  Of course somebody put it on something other than plaster, but for the most part it was a treatment on plaster and stone.  Calcimine paint is made from calcium carbonate (chalk), pigment, water and hide glue.  Recipes will differ but that’s the basic.  Lime wash is another paint that you may be familiar with, and that is made from lime that has been slaked (soaked in water for a long time).

If you have plaster walls, and you have calcimine or limewash paint on your walls and oil base or latex over it, you most likely have noticed it.  The chemicals in calcimine paint react (albeit slowly) with oil and latex paints and cause it to not adhere.  It takes many years.   Do you have those big chunks of paint falling off the walls, or see where it has and it was painted over?  Calcimine paint is most likely your  culprit behind it.  And nothing you can do short of taking that calcimine paint off the plaster wall will rectify the problem.  Fortunately for you, calcimine and lime wash are the easiest to remove.  Bad news for you, getting off the latex and oil based paint above it is a mess.

I’d also suggest you check out Peter Lord’s excellent post on Calcimine paint.  It give you much more detail on calcimine and how to strip it.

Varnish and Shellac

OK, you say these aren’t really paints, but they are solid coatings for wood.  If you have an old house, at the bottom of the paint covering your woodwork pray you have varnish or shellac.  It is going to make removing your paint that much easier.  They are your silent and unsung protectors of your wood surface from the ravishes of paint.  Most prewar houses had woodwork that was coated with varnish or shellac, rather than paint.  Why?  Because they used woods for the woodwork that was often a nice quality, nice looking wood.   Varnish and shellac showed off their beauty.  That’s one big reason you are stripping paint, right, to get that beauty back?

Once lesser quality wood was used for moldings and doors, shellac and varnish were not used.  People painted them, as the wood itself was not worth showing off.  If that’s the case with your house, say a mid-century modern, then you may have some work to do.  Because paint reacts differently with bare wood than with wood coated with shellac or varnish.


Next post:  understanding your surface and how paint reacts with it