paint advice

[Alasdair AllanParticipant @alasdairallan37423]

Hi I am new to the world of spray paint! I know to test combinations on scrap material first, before applying htem to my puffer but am still keen to get views about what combinations of paint and varnish should/ should not come near each other please.

Primer – I have used Tamiya mattt acrylic grey spray primer.

On top of this I have used wine red matt Humbrol spray paint on lower hull and will probably brush paint the upperworks with black acrylic humbrol.

Where I start to be less sure of my ground is what weathering materials and varnish should go on top of this.

My Humbrol brown wash says on the bottle it is enamel (the black wash doesn’t say what substance it is).

I have, onpast models. painted on clear polyeurathane varnish, but I was using enamel paint from tins then, so I am less sure about using this varnish now, as I would now be putting them on top of acrylic paint.  Not looking for insured advice, but any tips appreciated, thanks!

[ashley needhamParticipant @ashleyneedham69188]

Acrylic spray paint seems to be a minefield as regards compatability, with a lit of car xans being full of “other” solvents that react with almost anything else.

As far as I know, proper Acrylic paint from  tin should be OK.over an oil based paint, and vice versa for enamel over Acrylic. Polyurethane should be OK over any brushed Acrylic or enamel.

If you have used a spray then you will have to do the test thing I am afraid.

I use Acrylic craft paint, Rustins Acrylic primer/topcoat AND humbrol enamel and everything goes on no probs.

Ashley

[Richard SimpsonParticipant @richardsimpson88330]

I’m afraid it is not quite as straightforward as enamel or acrylic!  There is solvent based acrylics, such as the Tamiya rattle cans, and then there are the water based acrylics, which you can also get in rattle cans but which are also supplied by a number of suppliers, usually in the little squeezy bottles.  Then there is cellulose, oil based, polyurethane etc!

As a general rule of thumb you try to avoid putting a wash over a base paint of the same type as there is a danger that the wash can soften the base paint.  Pre mixed enamel washes such as Humbrol are fine over a solvent based acrylic, such as the Tamiya rattle can, as it is particularly resilient.  They can also be used sparingly over a Humbrol enamel base but only if the enamel is allowed to thoroughly harden.  I would give it a number of days, even a week to be safe, and even then don’t soak it for any length of time.

You have the general idea already, always do test pieces.  Be careful though, the test piece must go through exactly the same process as the model is going to go through so take care that temperatures are similar and drying times are the same.  Taking notes during the test process is invaluable.  Even humidity can play a part so, if you have some sort of electronic weather device make a note of the humidity as well.

I think the one thing more than anything that many modellers get wrong, and then go on to blame the paint rather than admit it, is not letting the paint harden properly.  That doesn’t mean dry to touch, that means the solvents have totally evaporated and the remaining solids are hard.  That can take longer than many allow for. I generally allow the following:

1) Solvent based acrylics: Fast drying and I feel quite confident of going over tham after a couple of days.

2) Water based acrylics: I tend to leave a little longer, three or four days as the water evaporates that bit slower.

3) Enamels: I frequently leave for a week before going over them with something else.  That may be over the top but I play on the safe side.

4) Oil based paints: There are model oil based paints available, particularly for weathering, which are very useful because they take so long to dry.  Consequently I wouldn’t go over them with any other type of paint for at least a couple of weeks.

Good preparation i.e. clean and dry, let things harden thoroughly before putting something on top, avoid too cold a temperature and too high humidity and you should have no problems.

[Alasdair AllanParticipant @alasdairallan37423]

Many thanks as ever for this advice. is Humbrol acrylic spray a solvent or waterb-ased acrylic?

[Colin BishopModerator @colinbishop34627]

Many thanks as ever for this advice. is Humbrol acrylic spray a solvent or waterb-ased acrylic?

Good point, I found an image online of the can which describes the propellant/solvent as extremely inflammable so it is not water based and you need to take Richard’s advice above.

Colin

 

[ashley needhamParticipant @ashleyneedham69188]

Late comment. Good last post Richard.

We can almost take away from this that Solvent acrylics and water based acrylics are different animals and not just ‘acrylic paint’ and should be treated with caution..

You should expand that into an article!

I only brush water based acrylics, Rustins Tins and craft paint.  I do have I think three plastic pots of Humbrol and Tamiya paints but they are not for boat use and almost never get painted over anything else although I have not had an issue with them over my craft tube paint.

Ashley

 

[ashley needham]

On ashley needham Said:

 

You should expand that into an article!

 

 

It would be a brave man who puts his head above the parapet for that one!  One thing guaranteed to bring all the keyboard warriors out of the woodwork is someone giving an opinion on paint!

Maybe I’ll feel brave enough one day!

[Alasdair AllanParticipant @alasdairallan37423]

finally… i have followed someone’s account of finishing off a puffer with a matt acrylic spray varnish called muntorium.  Obviously will test on paint before using, but in general does sprayed varnish of this sound solid enough for a boat that’s going to be in the water? I have my doubts, and may well end up going back to my favoured method of putting on polyurethane with a very wide brush!

[Colin BishopModerator @colinbishop34627]

My recent article in the December 2024 and January 2025 issues of the magazine on the subject of Modelling Materials covered paint and glue among other things including notes on varnishes including which type to use depending on what you are applying it to and what sort of effect you want.

The relevant bit reads as follows:

Varnishes sit alongside paints but instead of covering the underlying surface, allow it to show through and are very useful indeed. Traditionally they have been applied over wood to bring out and protect the attractive surface such as with yacht varnish. But they also have another role in protecting vulnerable surface finishes such as acrylic paintwork and applying a reflective surface finish which can be gloss, satin or matt as required. There are now some excellent crystal clear, non yellowing ‘varnishes’ on the market which can be brushed or sprayed. Many are intended for artworks. But do always check the specifications listing their characteristics such as waterproofing and UV resistance etc.

The rest of the article, including the section on painting and finishing, can be read in the magazine. The purpose of the article was to show what is available and things to think about rather than to definitively say use this, that or the other.

My current preference is for the Halfords spray Matt and Satin lacquers which go on over most substrates without problems but they appear to have stopped listing them. Fortunately I still have a couple of cans in hand.

Colin

[ashley needhamParticipant @ashleyneedham69188]

Alastair. Polyurethane yellows with age (unless you can get some guaranteed to not yellow) and generally this is where Acrylics score by staying colour fast .

I would say that almost any DIY store Acrylic varnish should be OK with the usual caveat of testing but I would have no hesitation in slapping on the Rustins clear varnish over anything. Considering the amount of time the boats spend in the water I have never had an issue with “indoor” varnishes, but it may be that they are more prone to uv rather than not being waterproof.

This is my personal experience and as Richard has said about parapet and heads….

EzeKote could also be considered…dries to a satin finish?

Ashley

[Colin BishopModerator @colinbishop34627]

Eze Kote is readily sandable so probably not hard enough for a hull side! I have used it to stick down and seal a paper sheet with printed planking onto a ply sub deck though.

To stick my own head above the parapet I have had some good results with Deco Art Duraclear which comes in matt, satin & gloss. Water based polyurethane and non yellowing. A lot of modellers and craft people rate it highly if you Google it. It does need a few days to fully cure though, rather like acrylics. It is weatherproof and water repellent so should be OK for hull sides but is not intended for long term immersion so probably best above waterline if you use the boat a lot.

Description below although it pays to shop around.

DecoArt Duraclear Matte Varnish 8oz

Rustins and Blackfriars traditional ‘oil’ based polyurethane varnishes are also excellent as Ashley says and can be applied over most finishes but they take a while to dry and are now quite expensive if you can find them as they are not now regarded as very environmentally friendly due to the volatiles in the tin. You need to use the interior variety as the exterior ones have UV inhibitors added which give a slight yellow tint. Lack of these inhibitors is neither here nor there for model boating purposes unless you leave your model on a south facing window sill for months on end!

Colin

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