What's American for 'undercoat'?
November 24, 2009 6:56 AM   Subscribe

Can someone give me a primer on translating the British terms for wall / house paint into their American equivalents?

I am no stranger to paint. At least, I wasn't until I moved from Britain to the US. Now I go into Lowe's Ace Depot and all the labels read "interior latex" and similar, which presumably makes sense to Americans, but doesn't help when I'm just looking for a tin of undercoat. Could someone with experience of doing paint jobs on both sides of the pond translate undercoat, gloss and emulsion into their American equivalents?
posted by holgate to Home & Garden (14 answers total) 2 users marked this as a favorite
Undercoat = primer
Gloss = oil-based paint
Emulsion = water-based paint
posted by xingcat at 6:59 AM on November 24, 2009

Also, paint in the UK is much, much thicker than paint in the U.S., so be prepared to apply more coats than you'd expect to here.
posted by xingcat at 7:00 AM on November 24, 2009

In the US, gloss and semi gloss refer to the sheen, not the oil-base.
Latex is water based and comes in all different sheens.
Behr brand hi-gloss paint will stay sticky for years. Use the semigloss in thin coats in you want a little shine.

Source: I hate hate hate painting closets and doors. Give me a nice flat wall and I'm good to go.
posted by SLC Mom at 7:48 AM on November 24, 2009

Undercoat = primer

See, that's where it gets confusing, because to me, primer is what you put on bare wood before undercoat and gloss. Is something like Kilz Primer the same as a British undercoat?
posted by holgate at 8:08 AM on November 24, 2009

I don't have the answer, but I know there's a whole hardware store chapter in I'm a Stranger Here Myself by Bill Bryson. It might cover paint, and if not, it might be helpful for the future. Or just humorous.
posted by necessitas at 8:23 AM on November 24, 2009

Primer and undercoat are different, even in the US. Primer is for surfaces that are unpainted, either because they are new or because they've been stripped. An undercoat is for surfaces that have an existing layer of paint.
posted by jedicus at 8:30 AM on November 24, 2009

Kilz is a mold and stain retardant product, although in some respects it is also simply a high-grade general use paint brand.

In the US, primer is what you put on bare wood, and paint is what you put over primer. I think most Americans would hear the word undercoat and think rust treatment on the bottom of a car. Still, read this: "An undercoat is always a primer, but a primer is not always an undercoat."

Maybe you could describe your particular conditions and we could advise you what to look for.
posted by dhartung at 8:33 AM on November 24, 2009

Sealer(sealant) is what you put on bare wood, so the Kilz is both. In most interior applications, you'd just do one or two coats of that over wood (or more likely, drywall) and then do your color. I don't know much about exterior applications, so I can't say what you would do then. I've used Kilz and it really does seal *everything* so it might be what you're looking for.
posted by fiercekitten at 8:34 AM on November 24, 2009

For the most part, folks in the U.S. consider primer and undercoat the same thing. It's a layer of paint underneath the final layer. For something on top of a layer of paint, you'd use what most stores call a "tinted primer," as most paint stores tend to think primer = white.
posted by xingcat at 8:46 AM on November 24, 2009

I'm a painter, (theatrical scenery and interior pretty stuff, mostly) and over the years I've found that terms for paint products vary across the US, and even from one hardware store to another. Terms I'm used to:

Primer: generally white latex or acrylic (pretty much synonymous) paint. Can be cheap and chalky, like a wallboard primer, or thicker with a slight sheen, like Killz or my preferred brand, Zinsser 1-2-3 primer. Wallboard primers tend to absorb the first coat of paint applied afterward, and they don't tend to cling very well to an already-painted surface. I tend to avoid them because I feel they're untrustworthy. Zinsser (available in water-based and shellac-based) is my go-to primer for any surface that's already been painted. It seals in stains and self-levels nicely, leaving a nice workable surface that won't require too many coats of color.

Undercoat: From my frame of reference, this is a term more often used by artistic painters & faux finishers. To me it means something like "a basecoat of color that isn't likely to be the dominant color once the project is finished." For example, if I was painting a landscape mural, I'd undercoat in a blue color to give a head start to the sky and some tone to foliage and things. Some interior house painters I know will use undercoats to help strengthen the hiding properties of a deep-colored wall. Something like undercoating in a pink before painting in a deep red. For a project like that, I'd choose just about any flat-finish or eggshell-finish interior latex product.

I'm also confused about this:
See, that's where it gets confusing, because to me, primer is what you put on bare wood before undercoat and gloss. Is something like Kilz Primer the same as a British undercoat?

In your experience, is the undercoat a matte-finish product? Does it have color? Is the gloss a clear product that only adds sheen or a protective layer, like or is it an opaque layer of glossy paint? To me, gloss as a term used alone means "a clear coat of latex or oil-based emulsion to protect and seal the surface, and add sheen." Synonymous with Sealer. Something like Minwax Polycrylic. If I just wanted a glossy white wall, though, I'd prime in Zinsser and do one or two coats on an interior latex gloss finish paint.

Note, too, that there is a difference between Sealer and Primer-Sealer. Sealer's what I described in the above paragraph. Primer-Sealer is a good quality primer, like Kills or Zinsser.

Whew. Long post. Does any of that help, or just raise more questions?
posted by alight at 9:53 AM on November 24, 2009 [1 favorite]

I saw that article, jedicus (and dhartung), and it fits with what I'd expect, but when I look for undercoat (i.e. for prepping painted surfaces), I get pointed to the primer/sealer, which seems a bit more specialised than the stuff I'm after.

My particular situation is that I'm looking to do the tradesman's trick of covering a stain on an ceiling with undercoat (or gloss at a pinch) before painting over it with emulsion. Yes, I could buy a dedicated sealer, but it'd be nice to know how to ask for a substance I'd recognise as undercoat, and this is just the most recent example of my utter bemusement in the paint aisles.
posted by holgate at 10:06 AM on November 24, 2009

To cover a stain, you want Kilz or a similar product. Tell the folks at the paint/hardware store what you are trying to do and they should be able to point you in the right direction.
posted by ssg at 10:21 AM on November 24, 2009

alight: this chart basically represent the mental map of "how to paint things" that's in my head. Undercoat is matte-finish in white or grey; gloss is opaque and tinted.

Primer-undercoat-topcoat (i.e. gloss/eggshell/etc) is what I'd use for woodwork and trim; for walls, I'd use an emulsion with perhaps a concealing coat of white for starters to "reset" a heavily tinted wall.
posted by holgate at 10:23 AM on November 24, 2009

Ok, that chart was helpful holgate.

It seems to me that an undercoat (to you) is just a type of primer (to us).

This is a pretty decent overview of primers, but it doesn't really address the variations in latex-based (emulsion) primers. The devil is in the details, there.

For unpainted wood, I'd apply two coats of a decent-to-middling quality latex primer before topcoating in one or two coats of interior latex, depending on the intensity of the color.

For an unpainted plaster wall, I'd do a coat of wallboard primer, which is cheaper and more chalky, to begin to seal the porous material. Follow that with a coat of a better primer, like Zinsser 1-2-3. Then topcoat with one or two coats of interior latex in whatever sheen you want.

For a previously painted wall, go with a good 'primer-sealer' like Killz or Zinsser. Look for products that are indicated with words like "high hide, strong cling, good bond," etc. Then topcoat with whatever you want.

At any rate, PaintTalk is an excellent forum for house painters. Search their archives for solutions and product advice.
posted by alight at 7:52 PM on November 24, 2009

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