How to seal acrylic paint?

[Bill97]

For the first time I am using acrylics on my new Cutty Sark build. Until this point I have always used enamels. I purchased an airbrush kit and am using Vallejo acrylic airbrush paints to do some nice effects on the deck and other parts. Once finished and thoroughly dry I want to seal the deck for protection with a matt or satin finish. What should I use? Do not know if I can put solvent based laquer, polyurethane, or other similar product over acrylics. Or, do I need to use some kind of water based top coat?  After all the work I have done getting the aged look to the deck I would hate to see it ruined by putting something wrong over the acrylic. Any help and advice would be greatly appreciated. 

[Roger Pellett]

Testor’s DullCote

[vaddoc]

You can use pretty much everything, wait a few days for a good cure of the acrylics. "Fat over lean". The toughest finish would be enamel varnish, I like humbrol. However water based varnishes are so much easier to use. The valejo polyurethane varnishes are nice but not as tough as enamel. Take care with matt varnishes, they can be tempermental

[jwvolz]

I second the Testor's Dullcote. I've airbrushed it over acrylics plenty of times. Just make sure they are fully cured (vs. just dry) and apply in light coats. 

[Bill97]

I have a can of clear spray lacquer on hand that I used to top coat the metallic copper spray I used for the lower part of the hull. I like to use it over the copper spray because the copper spray seems to be susceptible to fingerprints even after it is dry. Could I use that same product over the Vallejo acrylic Air?  I would do a test on scrap material to see if it is OK. Wondered if numerous very light coats with drying time between each would accomplish what I need. Do not want the acrylic paint to soften “melt” and ruin all the hard work I have done. 

[GrandpaPhil]

I use the Delta Ceramcoat Sealer.

[jwvolz]

3 hours ago, Bill97 said:

I have a can of clear spray lacquer on hand that I used to top coat the metallic copper spray I used for the lower part of the hull. I like to use it over the copper spray because the copper spray seems to be susceptible to fingerprints even after it is dry. Could I use that same product over the Vallejo acrylic Air?  I would do a test on scrap material to see if it is OK. Wondered if numerous very light coats with drying time between each would accomplish what I need. Do not want the acrylic paint to soften “melt” and ruin all the hard work I have done. 

It should be fine in light coats. I have put Tamiya clear flat lacquer in the spray cans over acrylics without issue. 

[Bill97]

Thanks everybody. Will do some test and see how it goes. 

[wefalck]

What is the purpose of this 'sealing' ?

[Bill97]

Wefalck, that is a good question!  One I just took for granted was necessary if using water based acrylic. Maybe I am wrong. Please enlighten me if so. As I mentioned in the beginning of the topic, this is my first time using airbrush water based acrylic. This is on the deck of my Cutty Sark build. Always used enamels in the past. I just assumed once I completed the weathering of the deck to my satisfaction that I need to seal it for protection from scratches or whatever. Again I just assumed acrylics were not as durable as enamels. Please tell me, if so, that I am wrong in that assumption and I don’t need to be concerned about it. The picture is my initial airbrush primer coat. More color and weathering will follow in additional coats and brush weathering. 

[Bill97]

Oh by the way, in the photo the deck is just setting on the hull, not glued in yet. I am doing the painting of the deck separate of the hull. 

[vaddoc]

If the acrylic paint is to suffer any abuse, it needs protection as it scratches easily. Otherwise, not really necessary unless a bit of shine is desirable.

[wefalck]

Acrylics typically take long to form a strong coating. There are two processes happening, the acrylics dispersion breaks down and the molecules begin to form an interlinked network and at the same time the 'solvent' evaporates, which becomes more difficult as the layer shrinks and the water molecules become trapped in it. Therefore, it may take several weeks before full strength is reached. It depends on the thickness of each layer that is sprayed on. Artist's acrylics (which includes modeller's acrylics) are made for decorative purposes, not for surface protection. Therefore, they may be not as scratch-proof as other types of acrylics.

 

For a working model, I would be concerned about the paint being scratch-proof and adhering very well to the underlying surface. For a stationary model this is not that much an issue in my opinion. It really depends on how rough your handling is during the building process. Personally, I delay painting as much as possible, until all parts are made and fitted.

 

Some modellers prefer a uniform sheen (usually matt or satin) all over their models. Again personally, I like to indicate different prototype materials by different levels of sheen (never really high gloss though). There may be a need to cover shiny spots of glue etc. over paint and in this case one may want to apply some varnish. In this case I would go for acrylics varnish, preferrably from the same manufacturer. Any unnecessary layer of paint might drown out surface details - airbrushed acrylics are really good to bring out surface detail, when sprayed on in thin layers.

 

Acrylics are quite forgiving, when it comes to mixing layers of different types of paint, if one obeys to some basic rules:

 

- spray thin layers to speed up curing - acrylics are pervious to water vapour, so water can evaporate through subsequent layers of acrylics; this may not be case when other types of paint are applied over acrylics, then water may become trapped and can cause problems with changing temperature.

 

- obey the old painter's rule 'fat over lean' (as noted above already); acrylics molecules are hydrophilic and would not stick very well on 'fat' oil paints or enamels, which are typically lipophilic; oil paint or enamel over acrylics would also trap any residual water (see above).

 

So in summary, unless you expect rough handling of your model during the construction or later, there is no need to 'seal' acrylics.

[Keith Black]

18 minutes ago, wefalck said:

there is no need to 'seal' acrylics.

 Eberhart, I would disagree only in that in time all paint is going to flake. By applying a protective coating (I use Poly) one is delaying that process. I think most modelers build for not their lifetime but for many more lifetimes to come. 

[wefalck]

But the flaking is mainly due to poor adherence to the surface. So that would not change with a an additional coating, just the flakes may be bigger.

 

Obviously I don't have a life-time experience yet, let alone that of several life-times , but I have spray-painted with acrylics a metal hull back in 1989 or so and it still looks like on the first day, thirty years later.

[Jaager]

Would shellac not also do the job? Not about resisting scratches, but an easy sealing layer.

Or conservators wax?

[Bill97]

Thanks again guys. Once completed the model will simply set on a display shelf. The deck should not receive any abuse or wear. Curious if during construction I would scratch it with tweezers, tools, are anything else and then need to touch it up and not be obvious. Again this is my first time to use it. I am a newby!

[wefalck]

I would not use shellac and waxes on acrylics. Their thermal coefficient of expansion are different. In addition, shellac is too glossy - unlike on wood it cannot be rubbed down on paint.

 

As for touching up: I avoid mixing paints, which removes the variable of getting the colour right. Of course, one would see touching up with a brush on a larger spray-painted surface. As I prefer to give my models a workaday look, the sprayed surfaces would be treated with washes (applied with a brush) of other paint anyway, so that touching up is not an issue.

[Bill97]

This is the Vellajo product I am trying out for the first time on the deck and on deck structures. So far I am really liking the effects. 

[wefalck]

I am using just their 'wood' colour as a basis and then apply washes of burnt umbra and flat black.

 

 

 

And this is the copper-plated hull painted thirty years ago:

 

[Bill97]

Wefalck do you like working with it. Your ship looks great. This product was recommended to me to try. So far so good. 

[wefalck]

Valejo paints are really high quality. Originally, they were mainly catering for professional artists and still do.

 

I never used solvent-based paints in my airbrush - too much messing around with organic solvents to get it really clean.

 

I prefer to use the pre-thinned paints for use in the airbrush. No worries about getting the consistency right. I also use these for brush-washes. For the latter, of course, the 'normal' paint range could be used, but I just keep one range in stock.

 

I found that these paints, when used for washes, behave very much like water-colours, but one has to be aware that they dry very fast and when dry cannot be redissolved (unlike enamels and freh oil-paint). This is both an advantage and a disadvantage, but I think more of advantage. You can work fast with acrylics, as there is virtually no drying time needed. You can apply one round of light washes, go for an espresso, and then can continue with the next wash without disturbing what you have done before. When using oils for this, as many do, you may have to wait for days in between applications, until the preceeding wash has sufficiently cured to be not redissolved by the next solvent-rich wash.

 

BTW, in the second picture I think I used a light spray of satin acrylic varnish to fix somewhat the white salt-stains applied with white pastel, brushed into the corners etc.

[Keith Black]

56 minutes ago, wefalck said:

But the flaking is mainly due to poor adherence to the surface

Come talk to me a couple of hundred years from now and I'll show you what I mean. 

[wefalck]

Well, the 2nd Law of Thermodynamics will get us all eventually

 

[vaddoc]

3 hours ago, Keith Black said:

I think most modelers build for not their lifetime but for many more lifetimes to come. 

This is a comforting thought Keith. I somehow doubt that my models will survive long after I am gone but who knows! 

[Keith Black]

3 minutes ago, vaddoc said:

I somehow doubt that my models will survive long after I am gone

I don't know why you would think that? Your work is very tidy and clean, top shelf stuff. I'm sure everyone in your family would be proud to display your work. 

[Keith Black]

2 hours ago, wefalck said:

the 2nd Law of Thermodynamics will get us all eventually

I am evolving, I spit on you, 2nd Law.

[Landlubber Mike]

I used this (the matte version) on some recent 1/72 plane models I completed and was really impressed by it.  They come in gloss, semi-gloss, and matte.  Goes on really thin and does a nice job.

 

[Bill97]

This is, I think, the finished deck before I put a matte or satin finish on it. This is with the Vallejo product I showed above. Trying to decide if I should lighten it a bit or leave it alone. Maybe to gray. Not sure. I also included a photo of the actual Cutty Sark deck for comparison. What do you think?

[BobG]

3 hours ago, Landlubber Mike said:

I used this (the matte version) on some recent 1/72 plane models I completed and was really impressed by it.  They come in gloss, semi-gloss, and matte.  Goes on really thin and does a nice job.

Mike, I often find that rattle cans have a tendency to "spit" tiny blobs occasionally even when I'm consistently shaking the can and wiping the nozzle. Did you have any problems like that using the the product you referenced? 

 

I'm going to be using Vallejo Air Acrylic paints to paint the hull of the Pen Duick that I'm building currently. It looks like the hulls of these racing sailboats have very polished finish. I've been wondering what will be the best way to obtain that kind of finish on the hull so this product may be a possibility. I'm not sure whether semi-gloss or gloss would be the way to go either.