Painting and finishing pine

[Brans]

Hello everyone,

Last year I built a garden table from scrap wood I found in company back yard and as you see on the picture below, I have sanded legs to 240, filled with P38 car body filler, sanded again, painted in three coats with woodies white paint and then put 3 coats of car clear lacquer. And as I can see it is still holding pretty good.

Now I am in a process of building two garden benches to match this table and after reading trough this forum i have couple doubts:

1 - Do I need to use the primer
2 - Do I need to use knotting solution or can I route knots 1mm and fill them
3 - What is a good external filler that can compensate all wood movements and won't crack (I used P38 car body filler from Halfords so far)
4 - Do I need to clean and fill line cracks that are full of pine resin

This is a photo of bench legs so far and they are also going to be white:

 

[MikeG.]

Brans, your approach to this is going to cause you some work in the long run. You are putting a hard, inflexible coating (car lacquer) over outdoor timber. It looks great initially, but over the years the wood movement and weathering will break this down in the way that undercoat and gloss always breaks down.

Your filler will be fine, and you could actually rout out the top of any knots or resinous cracks and fill with the same stuff. Not 1mm, though. Take out 6 or 8mm.

Welcome to the forum, BTW> I've just noticed you're new.

 

[Brans]

Hi Mike,
thanks for your advice.

First, when I built this table I wanted to see how certain things behave and work with wood (because I did not have any experience) so that's why I used car lacquer and I read on few other forums that can be used without any problems.

What would be your advice to use over painted wood?
Also is it necessary to use primer on raw wood as I have did not use any when painted these table legs?

Also is there some good exterior wood filler that I could use instead of car body filler?

On top of the table, I have used yacht varnish gloss and I have grey areas underneath now but I will seek advice for that in a separate post

Thanks

 

[MikeG.]

That car body filler as is good a product as you can use. Two part wood filler is pretty much the same stuff (some car body filler has a fibre reinforcement in it, I believe, which wood filler doesn't). There is no point looking for another product.

Primer? Not necessary if you are using an emulsion as a colour only under a following coat of finish. It is the top coat I am bothered about. In principle, all finishes for exterior timber should be flexible and "breathable" (allow the transmission of water vapour). Car lacquer doesn't do this.

 

[Brans]

OK, great.

One more question please

Is it necessary to use sanding sealer and will it make a difference in the finished product (smoothness, glossiness...)?

 

[MikeG.]

Under paint? No.

 

[Brans]

Great,

thank you.

 

[ED65]

MikeG, car lacquers are no longer the hard, inflexible coatings of old. They now have to be formulated so the same paint can go on the plastic/resin bumpers which are significantly flexible (much more so than wood) so car paints are now a viable option for painting wood.

 

[MikeG.]

Ooooh, right. Thanks. Time for an experiment then.

Vapour-openness would still be an issue, though.

 

[ED65]

1 - Do I need to use the primer
Arguably no, but it depends on what paint you end up using and how you apply it. The same paint applied in different ways can give different results. In the same way that one really thick coat isn't the same as the same thickness built up from 2-3 coats brushed out more thinly, three coats of a good paint straight from the tin vs a couple of diluted coats of the same, followed by two full-strength ones, last differently (the latter often giving far superior results, long term).

2 - Do I need to use knotting solution or can I route knots 1mm and fill them
I think it would be simpler to use knotting solution. In case you don't know, this is generally for live knots, dead knots are usually dealt with somehow although they can be left in situ.

If you're comfortable doing some routing of the surface then instead of filler you might consider wood patches, which are more assured to move with the wood. If you're familiar with "Dutchman" patches these would be that kind of thing.

3 - What is a good external filler that can compensate all wood movements and won't crack (I used P38 car body filler from Halfords so far)
Best of luck finding one o' those! Seriously this is the holy grail of fillers.

Not that P38 is a poor choice BTW, but you can't be sure the wood won't move more than it can handle. These days there's a lot of use of epoxy fillers, both commercial and DIY (made from various epoxies with wood flour or fine sanding dust). These deal o-k-a-y with movement, but they do tend to become obvious through paint over time, even on MDF apparently.

4 - Do I need to clean and fill line cracks that are full of pine resin
How fussy are you? It's largely a cosmetic concern. If their appearance bothers you then by all means scrape and fill.

 

[ED65]

Vapour-openness would still be an issue, though.

Ah yes exterior use, roger that!

 

[Brans]

Thanks for all the answers.

When I painted those table legs I applied three undiluted coats. First one was very thin and second and third ones were fully applied (but not too thick).
After that, I applied three coats of can spray car lacquer and it is holding very good so far (After one hot summer on one rainy winter).

For the resin, I am asking because I did not clean any resin from this table legs and I did not apply any knotting solution and I don't see any of those marks on the outside of the paint after one year.

As for sanding sealer, would it benefit if I apply it on end grain to stop wood from accepting moisture and water as this benches will be on the ground?

Also how much would you dilute those first two coats, is 50% fine?

 

[Doug71]

If I was going to that much trouble finishing I would probably consider buying some better quality wood to work with.

Sorry, that is not meant to come over as blunt as it sounds.

 

[ED65]

As for sanding sealer, would it benefit if I apply it on end grain to stop wood from accepting moisture and water as this benches will be on the ground?

Missed your question above about sanding sealer. No, you don't need to use it under paint. There are actually arguments for not using commercial sanding sealers at all but we won't get into that now :lol:

If you want to seal the end grain on the feet from water ingress epoxy is a better thing to use.

Also how much would you dilute those first two coats, is 50% fine?

It depends on what you're using how much to dilute by, if at all.

With a typical oil-based enamel I thin the first coat heavily. I do this by eye so not sure of the proportions but much more than 1:1 — the finished consistency is watery, not like a runny paint. It should readily sink into the wood and not obscure the grain.

With hand application (brush or roller) generally the advice is to thin less with each subsequent coat. The last one or two coats that are at "full strength", you may want to thin those just a smidge too. Be guided by the consistency of the paint you're using and how quickly it dries.

Many oil-based paints and varnishes benefit from a slight dilution to help them go on more smoothly and flow out better, but it depends on how it's formulated by the manufacturer. And maybe how long the tin has been open!

 

[Brans]

If I was going to that much trouble finishing I would probably consider buying some better quality wood to work with.

Sorry, that is not meant to come over as blunt as it sounds.

Don't worry I'm not that easily offended

I think that this wood was actually perfect because my intention was to use this table to see how will it behave and to be part of my learning curve.

 

[Brans]

As for sanding sealer, would it benefit if I apply it on end grain to stop wood from accepting moisture and water as this benches will be on the ground?

Missed your question above about sanding sealer. No, you don't need to use it under paint. There are actually arguments for not using commercial sanding sealers at all but we won't get into that now :lol:

If you want to seal the end grain on the feet from water ingress epoxy is a better thing to use.

Also how much would you dilute those first two coats, is 50% fine?

It depends on what you're using how much to dilute by, if at all.

With a typical oil-based enamel I thin the first coat heavily. I do this by eye so not sure of the proportions but much more than 1:1 — the finished consistency is watery, not like a runny paint. It should readily sink into the wood and not obscure the grain.

With hand application (brush or roller) generally the advice is to thin less with each subsequent coat. The last one or two coats that are at "full strength", you may want to thin those just a smidge too. Be guided by the consistency of the paint you're using and how quickly it dries.

Many oil-based paints and varnishes benefit from a slight dilution to help them go on more smoothly and flow out better, but it depends on how it's formulated by the manufacturer. And maybe how long the tin has been open!

Thank you very much for all your advice, I really appreciate them.