Difference between paint and stain

[Windows]

What’s the difference between paint and stain?

 

[sunnybob]

Stain is see through, paint isnt.

 

[Mike G]

Paint builds up a skin above the surface it is applied to. Stain is absorbed into the surface.

 

[Richard]

Stain is absorbed into the surface.

Not really. Strictly speaking only dye is absorbed into the wood's cells because dye dissolves fully (molecularly) in solution and therefore can bind with wood cells. Wood stain contains insoluble pigments that lodge in crevasses in the wood: frequently wood stain includes a dye in the mix, but the stain itself can't bind with the wood's cellular structure.

I blame the wood colourant manufacturers, certainly here in the UK that, for some reason, use the terms wood stain and wood dye interchangeably even though, in reality, they're different products. Typically, you can only tell you're working with a stain rather than a dye when the instructions for use indicate something along the lines that you should stir thoroughly before and during use to equally distribute the colourant (pigments) throughout the liquid. Dye never needs stirring before use. Slainte.

 

[Windows]

The first two answers matched my basic understanding of the terms. And then I came across opaque woodstain (specifically the Dulux version) and looked a little closer at previous stains I’d used and determined that pigment is deposited on the surface. So if lack of surface pigment and translucency are not characteristic of stain, what is stain? Is opaque woodstain stain or paint?

 

[Mike G]

Stain is absorbed into the surface.

Not really. Strictly speaking only dye is absorbed into the wood's cells because dye dissolves fully (molecularly) in solution and therefore can bind with wood cells. Wood stain contains insoluble pigments that lodge in crevasses in the wood: .....

Classic intermingling and mis-use of terminology by the manufacturers: cause confusion and chaos, but no matter, it sells stuff......

I'll stick with my original sound-bite difference, though. I think you've even confirmed it. Stain is within the surface of the wood, without creating a film. Paint (and lacquer and varnish), build a film. Now, you're certain to be right on the scale and location of the sub-surface location of the stain particles in comparison with dye, but in principle, both of them are below the top surface of the wood, and without building a film.

 

[Windows]

Skin-forming and non-skin-forming sounds a workable definition and matches my limited experience in the sense that the pigment on a stained surface is thin and seems more strongly bonded with the wood than adjacent parts of the pigment layer. I hope that manufacturers see it similarly. When I buy stain, probably my main motivation is that I want to apply colour but not at the expense of creating a layer behind which I could trap water.

 

[AndyT]

Richard has nailed it. Words which could usefully indicate what any product does have been mixed and muddled up so as to become almost meaningless when put on a bottle or tin of a commercial product.

It seems to be just as muddly in the US. I expect most of us have read some of the tireless work Bob Flexner does, sorting out what various manufacturers' products really are.

As far as I know, there's nobody doing the same job on products on sale over here. It needs to be online, to stay up to date, so I think it needs someone to do it as a labour of love.

Maybe someone with decades of experience in the trades, with a solid track record of teaching and published work?

Only if you want to, of course!

 

[Lons]

I view it in a similar way to Mike as in practical terms if removing paint you can strip it easily down to the original surface where if it's been stained it invariably has been absorbed and you have to take wood off to remove it.
The science bit is interesting but it doesn't really matter in practice as long as it "does what it says on the tin".

 

[9fingers]

.... it doesn't really matter in practice as long as it "does what it says on the tin".

Spot on Bob!
The OP should use whatever product to get the effect he desires irrespective of it's marketing description!

Bob

 

[Woodster]

I’ve used Chestnut Spirit stains quite a bit. They don’t seem to need shaking and soak deeply into the wood. I can’t say whether they bond with the cells or not but it certainly ain’t coming out!

From my experience many shed and fence products sold in DIY stores, sometimes called “stains”, are often just thin paint. :lol: Although in fairness there normally is a small shelf of exclusively brown stains somewhere in store.

 

[Windows]

The effect I desire is “has some colour and won’t rot for 15 years without maintenance”. What’s the product that’ll give me that?

 

[9fingers]

The effect I desire is “has some colour and won’t rot for 15 years without maintenance”. What’s the product that’ll give me that?

Coloured UPVC?

Seriously, no decorative finish on wood will last 15 years without maintenance. About the only exception would be proper creosote. I used this on my workshop in 2006 and whilst is has faded, there is not a trace of decay but dont expect this of retail creosote substitutes. You need full lead, real mans, creosote for that.

Bob

 

[AndyP]

I wish that I could find the youtoob vid of an old timer in his water powered workshop who was turning out round coopered cattle water troughs and other exterior paraphernalia. He said something that has stuck in my mind ever since. Paint is for decoration not protection. His argument was that the right timber in the right place will last longer unpainted than painted as due to natural wood movement causing the paint to crack moisture will eventually find it’s way under the paint “skin” and not dry out causing rot.

Problem is, in my mind, that few people can afford the right wood in the right place.

I’ve used cuprinol spirit based shed and fence preserver on all my outbuildings and gates for a long time. It wont last 15 years of course but only needs a stiff brush to get rid of the dust and dirt before slopping on a new coat every few years.

Just my two pennies worth.

 

[Windows]

Lot of good points. My recently formed and loosely held opinion is that paint is for interiors only.

I don’t expect any coating to keep its appearance in the elements for 15 years without touch ups or recoating, but I would like to know whether stained wood left untouched for many years will last as long as wood that has been left untreated under the same circumstances. My feeling is that unmaintained painted wood will fail earlier than wood that has never been painted. I’m hoping that’s not the case with stained wood.

 

[9fingers]

I fail to see how stain pure and simple will have any preservative effect on wood.
I tend to agree that paint on wood that subsequently fails could well accelerate decay in the wood as at some stage in the paint decay process, moisture and possibly bugs would be trapped.
New wood and Bedec barn paint is favoured by several here but will need regular maintenance.

Bob

 

[Windows]

It’s not so much a question of whether new stain protects wood as whether old stain can enhance the decay of wood. If I’ve got moderately durable wood that is expected to last 10-15 years untreated, would a single application of stain and no further maintenance be expected to reduce that 10-15 years?

 

[Richard]

I'll stick with my original sound-bite difference, though. I think you've even confirmed it. Stain is within the surface of the wood, without creating a film.

I haven't really confirmed what you originally said. The stain element of a wood finishing product in its original descriptive meaning, is insoluble pigment. As such those pigments don't penetrate the wood molecules and what they do is lodge in crevices, e.g., exposed pores in the vascular tissue, the coarser elements of ring porous species such as ash or oak, and so on. Frequently what's sold as stain includes dye which, as I said earlier, is a colourant that fully dissolves in the carrier, i.e., at a molecular level. And at this molecular level dye can be absorbed by the fibres that make up wood thus changing the colour of the fibres. Pigment can't do this and pigment stains include a binder, e.g., linseed oil, to help the pigment bind to the surface of the wood's crevices. Sometimes there's a clue in the product's description it being labelled dye stain which tells the user there is both dye and stain in the product.

Still, I suppose we're dancing on a pinhead because you're right to say stain changes wood colour, as does dye. It's just that the mechanism to effect colour change is different for each product.

One thing I did like about finishing products during the time I lived and worked in the US was that they had clarity of labelling for wood colourants. If the product was labelled dye, it was definitely dye, i.e., no insoluble pigments, and if it was labelled stain it meant it contained those insoluble pigments. I'm guessing that's still the case but I can't say for sure because I haven't lived in the US for nearly twenty years. Slainte.

 

[Doug71]

The first two answers matched my basic understanding of the terms. And then I came across opaque woodstain (specifically the Dulux version) and looked a little closer at previous stains I’d used and determined that pigment is deposited on the surface. So if lack of surface pigment and translucency are not characteristic of stain, what is stain? Is opaque woodstain stain or paint?

I use the spirit based version of Dulux Ultimate Opaque wood stain on all the exterior timber on my house and have been pleased with it.

It goes on really easily and looks just like a paint finish, what I like about it is over time it kind of wears off and fades like a stain rather than peeling like paint so is really easy to overcoat.

I think the external stain thing can get quite confusing. Some are categorised as low/medium and high build, the low generally being more watery like a preserver and the high build more like a paint or varnish.
The high build give more UV protection etc but are more likely to peel. If you read the small print on some off the peg external doors it states a high build stain or paint must be used.

 

[Trevanion]

15 years of zero maintenance is a big ask of any external finish, but not wholly impossible.

There are a multitude of factors but without a doubt sunlight/UV radiation is the biggest killer of finishes, a bit like human skin the timber can get sunburned underneath the finish if it does not offer the proper UV resistance like a sunscreen cream would for skin which then causes the finish to peel off from the timber. A well-applied finish on a durable timber could last 25 years without recoating so long as it is out of the sun and enclosed from the direct weather, like a north-facing window in a deep reveal. Paint forms a better "sunscreen" than stains because they are completely opaque and offer no path of light to the base timber, but are prone to cracking at the joints and letting moisture in behind the paint, though modern waterbased flexible micro-porous paints are much better than their ancestors in this regard.

I've seen windows made from Scots Pine with an immaculate factory-applied paint job last less than five years, that was a material failure (arguably a manufacturing failure, who in their right mind uses such a non-durable timber on the coastline?) where fungal rot has set in underneath the paintwork and it had all reduced to mush where you could poke your finger through the entire bottom rail of the sash to the inside with ease.

RogerM has done some long-term tests into Sikkens, Sadolin and Osmo.

https://www.thewoodhaven2.co.uk/viewtopic.php?f=27&t=519#p5004

https://www.thewoodhaven2.co.uk/viewtopic.php?f=27&t=2973&p=58136

Alternatively you could always go down the route of Snake Oil- ... sorry, I mean Linseed Oil Paint :lol:

 

[Mike G]

I've seen factory-applied microporous paint (white) last 21 years before needing re-coating....on south facing windows, including the cills and glazing bars. From the same manufacturer, black window paint lasted 15 years. The additional bonus is that re-painting involves no stripping or rubbing back. Just clean the surface, remove anything loose (it's unlikely there'll be any), and apply another coat or two.

 

[Windows]

Thanks for all the useful info. The long term test was very interesting.

Are there multiple brands of microporous paint? Does it come in gloss? Do you prime it first and if so does the primer need to be microporous too? Does it have any benefits when applied over existing finishes or do you have to go back to bare wood?

 

[Mike G]

When I asked the window suppliers what the nearest equivalent paint was that was available to the public, they told me Bedec MSP. Their factory-applied finishes are sprayed in ideal conditions, so inevitably perform better than brushed on paint done by an amateur, but Bedec MSP gives as near as you can get. There may be other manufacturers with similar products now.

No, you don't prime. You thin down the first coat, quite a lot. As with any paint, it's only as good as what it sticks to, so if you put it over another paint layer, it will fail when that original layer fails.

There are water-based gloss paints, but those aren't what is reccomended for exterior woodwork. I have no idea why. Bedec MSP comes in a satin finish.....so, semi-gloss.

If you are going to use it, pay close attention to the manufacturer's instructions, including the temperature range within which to apply it.

 

[Windows]

Thanks Mike. It looks like Bedec MSP comes in gloss (as well as satin) for some colours now.