oil based or acrylic primer

[discodever]

Hi, can anyone help me, what is the best primer for painting new wood, oil based or acrylic. Thanks.

[verne]

depends on what and where?

traditionally oil based were the paints of choice but that was in the days when they contained copious amounts of lead, cadmium and all sorts of other nasties. nothing could beat the performance of lead primer on any surface as part of a painting system that also used lead loaded undercoats and top coats... no longer commercially available as paint but the ingredients are if you want to mix your own and you can afford to buy in bulk...

there are still some nice bits of exterior woodwork that have stood up to british weather for a century or more only because of lead based paints... of course the timbers were better chosen for the jobs they had to do, plus having straighter grain and fewer knots and other weak spots and tended to be properly seasoned, back then also.

oil based is still the primer of choice for external timber, but only after treating the end grains (at least) with cuprinol or similar and treating any knots with patent knotting or shellac but it will not stand up as well with modern paints as it would have done with lead...

zinc rich primers are available and other metal based primers (red oxide and aluminium); although primarily intended for use on metal i have seen them used as wood primers without ill effect and probably to some good though i cannot comment further until i have lived a bit longer...

the success or otherwise of painting exterior wood often depends on the "painting system". don't think of the primer or the undercoat or the top coat in isolation from each other. they each are part of a painting system and each has its own job to do within that system that complements and enhances the qualities of each other. paint manufacturers go to great lengths to produce their system and you cannot do better than to start by consulting their literature or consulting their technical experts and using their recommended products...

the trade tends to use whatever is cheap and easy to apply...

when acrylic paint (to be used as an outside top coat) first hit our shores it was called ranch paint and probably for obvious reasons... one coat was supposed to be all it took to put a breathable waterproof skin over a fence or an outbuilding where warping of timbers, etc. wasn't a problem and it made it cheap and easy to recoat as often as was needed by unskilled labour...

it has developed much further now and as much of the trade is using acrylic inside as traditional paints, although i never have - yet! i have yet to see a tradesman using it outside even as a primer and i don't think i would even consider it...

[discodever]

Thanks for all you infomation you've been very helpful. PS it's for woodwork indoors. Thanks Again.

[verne]

it is still a good idea to show a lot of indoor timber some cuprinol - or at least some sort of woodworm treatment. a comprehensive treatment is best but to save money and time a splash on the end grains and the backs of skirtings, architraves and other similar timbers can only do good over the long term.

houses are not so well ventilated these days and this can lead to quite a lot of condensation and it is when the moisture content of timber rises just a little that it becomes vulnerable to attack by wood boring beetle or dormant eggs already in the timber can become active and continued climate change might affect all sorts of things in the future...

a great deal of britain is riddled with dry rot below ground and just waiting for a lack of ventilation and an increase in moisture to start growing and feeding near ground level...

it is a good idea also for best results to treat knots with patent knotting or shellac as sap can be exuded for years and years...

any new timber (or timber that is new to your address) that is intended to be worked or shaped that is to be part of a largely unsupported structure or totally unsupported should be stored (flat) for a few weeks in its new environment to normalize and allow the majority of twisting, warping and shrinking to take place before measuring and cutting and machining...

[painterman]

An oil based primer (not undercoat) will penetrate deeper than water based.

Oil and water don't mix,this also appplies to paint,though nowhere near as strict.

An all oil based system e.g oil based primer,undercoat and gloss is a very good sytem to use,in my view,the best.

Due to enviromental issues next year,whilst many oil finishes will still be available,due to the new paint regulations will contain far less solvent and carrier(the liquid that evaporates as the paint dries).

This makes oil based handle very differently.

For exterior wood oil based is the only way to go,water based hasn't caught up in terms of durability yet but it it's getting there.

[verne]

the majority of paints for industry and vehicles have become water based in recent years with traditional finishes becoming more unobtainable all the time. some vehicle manufacturers have been playing with the stuff for years and suffered a lot of problems for their pains. top coat laquer remains isocyanate activated for a tough finish as water based and single pack is still not durable enough. it is all a big nuisance.

it would be interesting to see how a 2 pack painting system would perform as general house paint. vehicle refinishing uses an acid etch primer to improve adhesion which is available as single pack or a two pack. i wonder if such a thing might be useful as part of a wood finishing system???

from time to time in the past i used polyeurethane based paints which were extremely durable and a worthy replacement for lead based stuff but these seem to have passed out of fashion also.

some mahogany veneered tops that had six coats of furniglass semi gloss polyeurethane varnish with wet flatting between coats had a glass like surface that was almost as hard... my local supplier says it is no longer available.