Oil and acrylic?

[Petemack]

Having recently returned to model building after many years I'm very interested in the advances that have been made in detailing and finishing of kits. In the painting arena I'm taken with the whole idea of the oil wash to bring out detail but can't shake off the art and decorating training that says oil and water-based paints don't like each other much.

In particularly I'm intrigued by the order in which one applies the oil wash to a model. It seems that many people add this wash after decalling but do you then go on to apply a finish coat, say a matt one, after the wash? If the paints are acrylic and the final coat is acrylic how does it react with the oil? My knowledge of paints says that acrylic should not be applied over oil. What do you do?

Perhaps the thinning of the oil prevents it being too sticky and most of it is in the panel lines etc but it seems to me any residue will undermine a topcoat that is water-based. What's the general experience in the application order of the finishing coats?

Cheers.

[Giorgio N]

Generally the steps I follow are:

- paint

- gloss clear coat

- decals

- another light gloss clear coat

- oils

- final coat in the desired finish (usually satin instead of matt but opinions differ here)

The oil paints I use can be thinned with water, however I've never had any problem with applying an acrylic varnish on top of these. One of the reason is probably that I always let plenty of time passing between any of these stages. This is not a deliberate technique but simply the result of not having enough time to dedicate to the hobby...

Regarding the decals, while the procedure above is the one I follow most often I sometime change if I'm using older thicker decals. In this case I apply the oils before the decals to avoid the washes to highlight the thickness of the decal.

[Petemack]

Thanks for your thoughts, Giorgio.

An oil paint you can thin with water …? Seems like a contradiction in terms! What make is that?

Good point about thicker decals and the effect of a wash. Must remember that.

I'm rather like you in terms of time. My current little project is proceeding at a snail's pace but I can see that, like you've found, it could have benefits in terms of the thorough drying between stages.

Cheers

[Nigel Heath]

Hi Petemack, the steps I follow are similar to Giorgio's but slightly different:

- paint (enamel, acrylic or lacquer based)

- gloss clear coat (usually actual Klear so acrylic based)

- decals

- another light gloss clear coat I normally don't bother with this step and have not had any disasters, I like to minimise the number of coats on models as much as I can to try to preserve detail, it has nothing to do with my laziness honest

- wash using diluted artists oil paint - let that harden up overnight

- final coat in the desired finish (usually matt or satin acrylic varnish, depends what it is)

- Take masking off windows and add final details

- Stand back and admire your handiwork

In my experience you can apply acrylics on top of enamels and visa versa. The one to be careful with is cellulose based paints like Alclad, the solvent is very "hot" and can cause paint underneath to craze. You can even get away with this if you apply very light coats and let the solvent evaporate before it has a chance to react with the underlying paint.

Most of the above assumes you are using an airbrush but would broadly be applicable to brush work as well.

I hope that helps.

Nigel

Edited January 14, 2014 by Nigel Heath

[Petemack]

OK, that all makes sense. i suppose it's the artists oil colours that cause me the most concern. As a painter my knowledge of oils is that their slow drying characteristics mean that they tend to shrug off other finishes - for example,look at the paintings of Jackson Pollock who mixed all sorts of different paints on the canvas, many of which are disintegrating as the years go on. Or any old masters that were painted without careful regard for the different drying times of successive coats that have crazed and cracked. The rule was/is 'fat over lean' ie the paint with least oil is at the bottom and to be stable the next coats can be the same or oilier but not the other way round.

I can see that careful of application of acrylics and enamels could be fairly safe as they both harden quickly and your point about hot solvents is well made. Artists oils essentially never harden (though they may 'skin' to some extent) and that's the bit I find hard to reconcile. Do you take steps to remove residue with a degreasing solvent from areas that don't need to display any signs of wash before applying acrylic? Does the acrylic coat stand up to handling over time if an oil wash is below it? Or maybe the fact that a carefully finished model gets very careful handling means that the finish doesn't get bruised or worn and remains relatively untested for stability?

Cheers.

[Nigel Heath]

You raise some interesting points Petemack, I think you may be overthinking it and your artistic training is misleading you a little. The oil washes are artists oil paints diluted to a watery consistency with white spirit. This then allows the thin fluid to flow into details like panel lines via capillary action. The solvent evaporates quite quickly, say half an hour or so, so you are left with a very thin deposit of oil paint in the details. The excess wash can then be wiped off, I just use dry tissues. This leaves the oil paint in just the recesses that you are trying to highlight. Leave that to harden up overnight. The film of oil paint is so thin that the linseed oil in the oil paint has enough time to cross link and become dry. The diffusion time for a micron thin film like this will be many orders of magnitude shorter than that required to set thick splodges of paint like on a Jackson Pollock work so the oxygen in the air will easily cure it in this time. Water based paint will cover this solid deposit of wash quite happily.

A varnished model is quite robust and handlable, don't forget that the wash is only in recessed areas so is very protected from mechanical damage.

You can make washes using acrylics of course but I think oil paints give a better finish and are more forgiving to work with.

Best thing to do is have a go - it is the best way with modelling

[Giorgio N]

An oil paint you can thin with water …? Seems like a contradiction in terms! What make is that?

I know, sounds strange... they are the Artisan line from Winsor & Newton,

http://www.winsornewton.com/products/oil-colours/artisan-water-mixable-oil-colour/

I have to say that the pigment is probably not as fine as in other high end oil paints, however the possiblity of thinning them with water made them better suited to my modelling table when I started experimenting with washes... strange thinners, no smell in the living room !

Now I don't have these problems anymore but I still have the same paints I bought back then so I'm using these rather than buying others

[Petemack]

Giorgio - very interesting. I'll have a look at those.

Nigel - Completely right, I probably am over-thinking and being over-cautious. Your explanation and experience is the sort of thing I hoped to hear and it makes good sense. I just hadn't seen a discussion of the issue anywhere else.

Time to get the (air)brush and paints out, methinks.

Thanks all.

Pete