Acrylic vs oil based paint durability

[jabell]

No doubt this has been raised many times, but couldn't find anything recent, so here goes (again!).

Ignoring all the arguments about ease of use etc which are well known, I'm looking to see what evidence there may be that in external situations that acrylics have better durability than oil based paints. Time has come to yet again repaint my verandah posts and barge boards, which I have done traditionally using an oil based pink primer, oil based under coat, and two oil based top coats.

Appearance is excellent of course, but the long and short is that after so many years it breaks down. So was all this pedantic effort worth it? Perhaps an acrylic would have lasted the same amount of time without all that effort?

If I give the acrylics a go, and it also breaks down in a few years and decide to revert to oil based again, have I burnt my bridges and have to scrape it all off before returning to the traditional sequence?

I really don't mind the labour, the smell or anything else other than durability.

[rob streeper]

Oils, good lines that is, still outlast all of the water based products. There are UV protectant agents available separately for some types of paints, check compatibility.

Cheers,
Rob

[graham.murfett]

I now only use oils on interior stuff.
I have good success with Acrylic weathershield type products.
More coats with a low mm nap roller, rather than less coats with a brush over flat surfaces.
But that's me.
Oils always look better.

[jabell]

Oils, good lines that is, still outlast all of the water based products. There are UV protectant agents available separately for some types of paints, check compatibility.
Cheers,
Rob
Hi Rob, do you know of any test data on this? Perhaps paint companies do not publish such info in their self interest given the attractiveness of the ease of acrylics. As for finish oils are demonstrably superior, and all I will use in interiors, but it might just be that both are as bad as each other in exposed weather, at least until some superdooper nano-technology creeps into the industry.


I was a building inspector for ten years, and it amazed me the number of people who wanted that external natural timber look, and then varnished it all with Estapol, or in one case very expensive varnish from Finland(what do they know about sun???).
Looked great on day one, but all of them were dreadful two years later.


I was hoping there was some standout acrylic that last double that of oils, but I guess not.
cheers
John

[justonething]

No doubt this has been raised many times, but couldn't find anything recent, so here goes (again!).

Ignoring all the arguments about ease of use etc which are well known, I'm looking to see what evidence there may be that in external situations that acrylics have better durability than oil based paints. Time has come to yet again repaint my verandah posts and barge boards, which I have done traditionally using an oil based pink primer, oil based under coat, and two oil based top coats.

Appearance is excellent of course, but the long and short is that after so many years it breaks down. So was all this pedantic effort worth it? Perhaps an acrylic would have lasted the same amount of time without all that effort?

If I give the acrylics a go, and it also breaks down in a few years and decide to revert to oil based again, have I burnt my bridges and have to scrape it all off before returning to the traditional sequence?

I really don't mind the labour, the smell or anything else other than durability.
I know its easy to do headline comparisons of water vs oil based paints. But the reality is that these are paint systems applied to the substrate underneath to form protection regimes and should be looked at holistically . Having said that, acrylics and alkyd based paints do have different headline properties. latex is flexible and is therefore more suitable where there is a fair amount of seasonal movement in the substrate. Alkyd is much harder and resistant to scratches and is therefore suitable for substrates that are often subject to abrasion or traffic. My experience has also shown that oil based paint on one hand provides more adhesion than latex but on the other hand become brittle overtime under the Australian sun much more readily than latex.

Many years ago I worked as a graduate engineer at one of the Railway Corporations. One of the things we did was painting. Lots of painting, stations, bridges. We always used oil based in those days. High traffic areas require hard wearing surfaces that only Alkyd paint could give. But we were continuously painting to make sure the Alkyd paint didn't have time to deteriorate to an extent that require extensive work - much more frequently than in a domestic environment.

One of the major problems in painting is the lack of surface preparation and the understanding of the conditions under which paint will stick.


Preparation of substrate: If there is any dirt or dust at all, it wont stick. Also while latex can go on top of an oil paint surface the opposite should not be done because when the latex expands and contracts it will crack the oil based paint on top.
The primer-undercoast-topcoat system is a simplification but is essentially necessary. I know there are now paints that you are claimed to be all in one, so there is no need to use a primer. However dont expect these to last because it is a compromise. Primers are meant to provide superior adhesion to the substrate and a key for the next layer. A lot of primers can also be sealer that would stop the leaching of oil/dye from the timber. Undercoats provide masking and filling purposes which are generally not needed for latex but they still have a place in oil based systems. Top coats provide the ultimate protection against the elements as well as traffic.
All previously surface should be thoroughly cleaned and roughen to provide a key for the next layer.
There are different primers for porous and nonporous surfaces. Wood primer should be used for bare wood only. Painted surfaces can also be primed, but with a special primer (https://www.bunnings.com.au/gripset-betta-1l-super-primer_p0960180) for non-porous surfaces to improve adhesion.
For any kind of newish external structure I'd use latex because the structure is likely to expand and contract as the timber dries and acclimatize to the local environment unless it is a high traffic area or it is a windows. If the house is old, then oil based would be just fine.


Finally if paints are coming off, it is more likely to be due to ineffective preparation more than anything else.

[jabell]

Thanks for such a detailed answer.
In my travelling 20s, I spent a few years in London like so many of us, and took up house painting with a mate to make a living, and we became pretty good at it, both in the quality of our preparation and in the finish, which paid off because all our work was on recommendation.

Consequently I never took shortcuts in my own home, an 1880s settlers cottage in the Adelaide Hills that gets both the freezing cold driving rain of winter and the heat of summer, always prepping the timber well and the four coat oil based paint system. Even the backs of all skirtings, architraves and barge boards got primed.
405545
But weather always wins of course. What I've particularly picked up from your comments is that if I re-coat externally with acrylics now, then there is no turning back to alkyds next time around, so I'll stick with Plan A.

[justonething]

Beautiful house :2tsup:

[rob streeper]

Hi Rob, do you know of any test data on this?


John,

Not off the top of my head. I understand that the number of paint manufacturers in the US has been reduced to three because of consolidations and acquisitions. Pittsburgh paints used to have a test facility in south central Pennsylvania that could be seen from the highway but I've never encountered a durability comparison between manufacturers.
I use both Sherwin Williams and PPG paints and I think Sherwin has the edge in the water based products. The SW oils are very robust - never had a call back about durability. The PPG oils are nice but different, they don't flow out quite as well IMO but durability is also excellent. SW and PPG may be sold as different brands in Aus if they're sold there at all.
You may also consider using marine grade paints - they are typically extremely weather resistant but I'm not familiar with them beyond marine spar varnish.
I wouldn't use oil over acrylic either, I've seen a number of very bad incompatibility problems.
Cheers,
Rob