4 ms·

one thing i’ve learned from doing little home improvement projects over the past few years is that paint is a 2-part product, primer and topcoat, and neither sh

one thing i’ve learned from doing little home improvement projects over the past few years is that paint is a 2-part product, primer and topcoat, and neither should be skipped if you want good results. generally speaking, primer sticks and seals while topcoat colors and protects. this isn’t made obvious in any way to the novice, and big box store workers seem as ignorant about it as anyone.

mauvehaus 6y ago
Depending on the application, the primer coats can fulfill a couple other requirements as well: If you want a really smooth topcoat, you usually want to sand past what you can reasonably/economically/effectively do on the substrate. Some primers are formulated to sand nicely to a powder (as opposed to balling up in clumps on the paper). You'll see this spraying higher quality paint grade work. You have to have a decent surface before you prime, but the primer can really smooth it out for the topcoat. If you're finishing pine with knots in it, you'll want a primer that will seal the knots, otherwise the pitch will eventually bleed through and discolor the topcoat. Shellac excels at this. Shellac is also outstanding as a sanding sealer. You can use that in a couple of ways: to fill the pores in the wood so they don't get full of sanding dust (which can be key if you have inlay of strongly contrasting woods), or to stiffen the fibers of softer woods so you can get a better/smoother sanded surface for the next steps in the finishing schedule. Shellac is also often used as a barrier coat between otherwise incompatible finishes or when you have a relatively fragile stain layer. If you're putting an oil based finish over an oil based stain, you run the risk of picking up the stain as you apply the topcoat, especially if you're brushing or wiping the topcoat. Because the solvent in shellac is alcohol, you can pretty freely brush it over oil or water based stains without risking a disaster. And yes, I do use primers other than shellac from time to time if I have a specific need, but dewaxed shellac is compatible with basically everything, so I always have a can around. N.B. I'm not a professional finisher. Don't take my word on any of this; test your prep and finishing schedule on scrap!
- clairity 6y ago
  > “If you're finishing pine with knots in it, you'll want a primer that will seal the knots, otherwise the pitch will eventually bleed through and discolor the topcoat. Shellac excels at this.” yes, i learned this the hard way, albeit on a simple set of wall shelves as cat stairs that i can easily fix eventually with shellac and another topcoat (when i get around to it).
kube-system 6y ago
And that's just for home improvement store paint. More sophisticated painting processes, like for automobiles, can be 5+ different types of coatings. i.e. electroplate > primer > base > mid pearl > clear
korethr 6y ago
The big box stores employees at the paint counter seem as ignorant as a novice about the vagaries of application most likely because they themselves are novices. They may know quite a bit about colors and matching and how to work the mixing machines, but they probably don't have much more experience painting than the average homeowner. That knowledge comes more from doing, whether its a handful of projects as a homeowner, or regularly as a professional. IMO, the stores could do better about offering basic information about this, about when one would need a primer, or just a topcoat, what kinds of paint bases are appropriate for what applications, what kinds of application methods are appropriate, etc. Instead, the response of the big box stores seems to be to skip the question entirely with combined products, e.g. "paint and primer in one".
- clairity 6y ago
  yes, there's no experience or incentive for better knowledge in big box stores unfortunately. i've moved on to buying from a local paint specialty store, which is owned by a family that i believe is/was in the construction/painting business. they cater mainly to contractors but also sell to the wider public. oh, and yeah, paint and primer in one does neither job very well.
  - korethr 6y ago
    As someone who's painted professionally, I can confirm the truth of this.
  - renox 6y ago
    Yep, been there too: paint is really something where you want to avoid the big shop and goes to speciality stores instead (paint peeling from the wall? Color changing after a year? Done and done --> switched to a dedicated paint store == no more issues, the paint itself is more expensive sure but the result is stable)
    - loonster 6y ago
      Paint peeling could also be a humidity issue. I had paint peeling on my ceiling due to water problem in the basement.

mauvehaus 6y ago

Depending on the application, the primer coats can fulfill a couple other requirements as well: If you want a really smooth topcoat, you usually want to sand past what you can reasonably/economically/effectively do on the substrate. Some primers are formulated to sand nicely to a powder (as opposed to balling up in clumps on the paper). You'll see this spraying higher quality paint grade work. You have to have a decent surface before you prime, but the primer can really smooth it out for the topcoat. If you're finishing pine with knots in it, you'll want a primer that will seal the knots, otherwise the pitch will eventually bleed through and discolor the topcoat. Shellac excels at this. Shellac is also outstanding as a sanding sealer. You can use that in a couple of ways: to fill the pores in the wood so they don't get full of sanding dust (which can be key if you have inlay of strongly contrasting woods), or to stiffen the fibers of softer woods so you can get a better/smoother sanded surface for the next steps in the finishing schedule. Shellac is also often used as a barrier coat between otherwise incompatible finishes or when you have a relatively fragile stain layer. If you're putting an oil based finish over an oil based stain, you run the risk of picking up the stain as you apply the topcoat, especially if you're brushing or wiping the topcoat. Because the solvent in shellac is alcohol, you can pretty freely brush it over oil or water based stains without risking a disaster. And yes, I do use primers other than shellac from time to time if I have a specific need, but dewaxed shellac is compatible with basically everything, so I always have a can around. N.B. I'm not a professional finisher. Don't take my word on any of this; test your prep and finishing schedule on scrap!

clairity 6y ago
> “If you're finishing pine with knots in it, you'll want a primer that will seal the knots, otherwise the pitch will eventually bleed through and discolor the topcoat. Shellac excels at this.” yes, i learned this the hard way, albeit on a simple set of wall shelves as cat stairs that i can easily fix eventually with shellac and another topcoat (when i get around to it).

kube-system 6y ago

And that's just for home improvement store paint. More sophisticated painting processes, like for automobiles, can be 5+ different types of coatings. i.e. electroplate > primer > base > mid pearl > clear

korethr 6y ago

The big box stores employees at the paint counter seem as ignorant as a novice about the vagaries of application most likely because they themselves are novices. They may know quite a bit about colors and matching and how to work the mixing machines, but they probably don't have much more experience painting than the average homeowner. That knowledge comes more from doing, whether its a handful of projects as a homeowner, or regularly as a professional. IMO, the stores could do better about offering basic information about this, about when one would need a primer, or just a topcoat, what kinds of paint bases are appropriate for what applications, what kinds of application methods are appropriate, etc. Instead, the response of the big box stores seems to be to skip the question entirely with combined products, e.g. "paint and primer in one".

clairity 6y ago
yes, there's no experience or incentive for better knowledge in big box stores unfortunately. i've moved on to buying from a local paint specialty store, which is owned by a family that i believe is/was in the construction/painting business. they cater mainly to contractors but also sell to the wider public. oh, and yeah, paint and primer in one does neither job very well.
- korethr 6y ago
  As someone who's painted professionally, I can confirm the truth of this.
- renox 6y ago
  Yep, been there too: paint is really something where you want to avoid the big shop and goes to speciality stores instead (paint peeling from the wall? Color changing after a year? Done and done --> switched to a dedicated paint store == no more issues, the paint itself is more expensive sure but the result is stable)
  - loonster 6y ago
    Paint peeling could also be a humidity issue. I had paint peeling on my ceiling due to water problem in the basement.