Surface preparation

[AVB99]

Please forgive the basic nature of this question. Have just stripped, for the fourth time, the chassis of my Revell 1/16 Model T Ford as the finish, which I'm determined to make perfect, wasn't up to scratch. By strip I mean that I removed thw Klear then the black gloss and then the primer - taking it down to the plastic again.

On Friday I received a polishing stick from John's shop and it's amazing - never used one before - have always used a high grit stick.

When i was sanding down the now stripped chassis, I did a small area of what will be unseen and then finished it with the polisher which gave an amazing finish. My question is this - when preparing a surface to receive primer, should the surface be very, very slightly course or is a highly polished surface better? I'm thinking of the ability of the paint to cling to the plastic.

Thanks

Aidan

 

[Ian M]

If this makes sense; you need a surface that is as smooth as you can get it but with out a shine. Shiny = slippery and the primer might loosen. A hot primer (spirit base) might etch enough to grab hold but acrylics might just dry onto the surface and then lift off later. (normally after you have painted, decaled, weathered and sealed the model).

The most important thing is to make sure the surface it grease and dust free.

A rub down with an ultra fine wet and dry, or a polishing pad will give a great surface, then a rub down with a fluff free cloth damped with a soft spirit (that will not attack the plastic). to remove the finger grease and the dust from the rub down.

latex gloves are a must from this point on. (OK I write what you should do, not what we actually do... )

Ian M

 

[AVB99]

Thank you Ian - this is exactly what I am doing. I shall avoid the tempttaion to shine the surface with a polisher.

Aidan

 

[tecdes]

Aidan I would only use the polishing stick for the simple reason that it is a polishing stick used at the end of operations not at the start.

Do not know which paints you are using ie oil acrylic & which in these category in detail so the answers, with out that info, are going to be basic & a little speculative.

I use Vallejo & this is my method. I wet & dry with a worn paper 1500 gauge using the paper wet. Use a large soft brush with water & gently wash down to remove the haze made by the wet & dry.

Dry & then give a good brush to get rid of any little bits left. I perform this away from the airbrushing area otherwise the bits just drift back down.

I then spray on a mist coat of Vallejo primer which come in a multitude of colours. Then followed by a full coat. Vallejo has water based resin which is the "glue of the paint to the strata. I use about 25% Vallejo thinners which also contains the resin. If you use water as a thinner you thin the "glue" in the paint. Vallejo is self leveling & is very forgiving if you apply to much paint. In 9 months not had puddle lump form.

Then wet & dry & apply Vallejo Air. Normally 2 coats they say 4 for the best finish.

I use Vallejo gloss varnish in preference to Klear which I have found much better in so many ways. Decals apply perfectly. Then Vallejo varnish matt satin or gloss as the mood takes you.

Vallejo say you can you can use all manner of paint films over Vallejo once of course the paint film has fully cured. But I would first experiment on an odd piece first & make sure the decals were fully protected with varnish.

Aidan this is for Vallejo only as other paints have similar but differing properties. I found there was a great divide on this score between Acrylics & Oil. One thing there is no substitute for skilled preparation work. Takes immense time, comparatively, but pays great dividends.

Also if you have used blue tack then spray over that area later make sure you clean the area with airbrush cleaner. Latest piece I have sprayed is now mottled in the area of the blue tack. White tack is not a problem

Laurie

 

[AVB99]

Laurie many thanks for a detailed reply. I am using acrylics, vallejo grey primer and humbrol gloss black paint. I like the idea of a mist coat of primer. I intend spraying the klear next time rather than brushing but if that fails will switch to vallejo varnish as the vallejo primer is so good. I think part of my problem has been with the brush application of the klear. Chaps on here say that i should not allow it to pool in corners. This may be making me apply too little. I know it's trial and error but it's very irritating ar times!

Thanks again

Aidan

 

[tecdes]

Two things Aidan.

First I found spraying Klear not as good as brushing. When brushing Klear I found that very little often on the brush is best rather than blast it on in large doses. Then give further coats then you do not get puddling. If I got a puddle I carefully wicked it with a bit of kitchen paper making sure it did not touch the plastic. But others may give you a more Klear idea (sorry).

Second which I should have included in my above "essay" (sorry). The temptation is to dry the acrylic as soon as possible. But found, as Vallejo is self leveling, that it is best to not dry to quickly as it needs time to level & also not to have to higher temperature as the paint starts to dry in the air or directly it hits the plastic. Get it right for self leveling & the finish is absolute in it's smoothness.

If you use the Vallejo varnish really make sure you give the airbrush a good & thorough clean as it is very naughty otherwise.

Sunday sermon finished.

Laurie

Just read your original article. I would take a bet that the primer was not dry.

 

[AVB99]

Laurie please do not apologise for the length of any posts. I am deeply grateful to you and all of the other guys who give of their time and experience to assist newbies like myself.

You may be right about the dryness of the primer - I really cannot recall. Last night I gave the surfaces their first coat of primer. I have just given the secnd coat so that's about 15 hours apart. I shall wait until Tomorrow evening before lightly sanding the primed surfaces and applying the first coat of airbrushed gloss. I shall then, if the coats looks ok, wait until Tuesday evening before applying the second coat. Am I right in thinking that I should give a light sand to the first gloss paint coat when it's dry please?

Regards

Aidan

 

[stona]

Good advice above.

Most of my models get a light sanding as part of the assembly process! Once I've blended a seam for example it is easy to give the rest of a wing or fuselage a quick swipe. This is a very LIGHT sanding. I'm not (usually) trying to remove or soften the hopefully crisp detail created by the manufacturer in their fantastically expensively produced mold.

I sand my primer with a worn high grit sand paper too. I wear the paper by rubbing it on itself....simples,usually 2500 but a worn 1500 should be fine. This will leave the surface of the primer feeling quite smooth but it does have a minute key for your paintwork. Some people prefer a wire wool for this stage.

It's really important to leave coats of whatever you've applied for plenty of time before assaulting them with anything even mildly abrasive.

Patience is the cheapest but most important tool in the box.

As far as sanding gloss paint it would depend on the paint. I've sanded enamel paint finishes which tend to be tougher than acrylics but only to help erase slight mistakes at masking edges for example. If the paint is well applied I don't see why it would need any kind of sanding or polishing.

Cheers

Steve

 

[tecdes]

I would have given the primer a bit more drying time, Aidan, especially as it is acrylic & you are, I have assumed, going to use gloss oil over it. Or another acrylic manufacturers paint. Not a a great advocate of mixing paint manufacturers as it increase the risk of disaster or at the least perhaps minor difficulties especially drying.

That is you hardly have to wait for Vallejo to dry & recoat (with Vallejo) as the undercoat will dry thro. the top coat.

Others may help on drying times as I only use Vallejo.

Hope you get on OK let us know.

Laurie

 

[AVB99]

So do you think 24 hours is enough drying time for the vallejo acrylic primer before I add the first gloss acrylic coat (Revell - I was mistaken when I referred to Humbrol above)?

Regards

Aidan

 

[tecdes]

Not brave enough to answer that question Aidan.

I think I would leave it 48 hours to be reasonably certain. Primer is the most difficult paint to predict as it is a paint applied to a different background than the paint whilst the following coats are on average acrylic on acrylic or oil on oil. Also the humidity & temperature both play an essential part.

A wealth of information is available on the Vallejo site click the Union Jack unless you read Spanish. vallejo: downloads. Go for FAQ's.

Laurie

 

[AVB99]

Hello

I have lost count as to how many times I have stripped my Model T Ford back to the plastic becasue of problems with Varnishing.

I have now sprayed a coat of Vallejo Grey primer which looks good. Am now going to try Vallejo gloss black paint.

Please - is it best to add water as a thinner or the Vallejo thinners? And, please, what proportions?

Thanks as always

Aidan

 

[BarryW]

I am another Vallejo user though I do not use gloss colours as I prefer to gloss varnish glossy areas. I would always use the Vallejo thinner because it is specially formulated.

 

[tecdes]

Afternoon Aidan

I always use Vallejo thinners. This has acrylic resin in it the same as the paint constituent medium. I have looked at water & thinners together & the thinners looks thinner than water. Also does not have, forgotten the correct expression, tension on its surface as water has. So I think the thinners is better than water.

How much is a difficult question. Lot depends on the airbrush, the size of nozzle & temperature.

Assume you are using Vallejo Model & not Model Air as I do not think that gloss is obtainable in Air. Air being airbrush ready but even then I thin 40 to 50 % with a .2 nozzle neat with a .4 nozzle

Model Air was originally for hand brushing but as Vallejo say can be air brushed. But the Model stuff is about twice as thick as Model Air. Just compare the weight of a bottle of each. When I have used Model I have had to thin about 60% to get it to work. But that is my set up others seem to use it well with an airbrush. Problems is if you thin a lot your gloss finish is going to suffer.

I would experiment with it on a discarded plastic drink bottle. Think this is the only way of finding the optimum paint/thinners mix for your set up. Like Barry I use Vallejo Varnish but not sure you would get the gloss finish you hope for as with gloss black.

One thing you need to be carful with Aidan. Acrylic matt is very forgiving. With gloss preparation is of prime imortance as defects & pimples will show up in the light reflected by the gloss paint. So wet & dry the surface with very fine paper & after dry use a tack rag or brush to get rid of debris.

Laurie

Add this addition as some one is bound to pick me up on it.

All work should be wet & dried to remove pimples etc before the next or final coat. But gloss needs more attention like perfection.

 

[AVB99]

Laurie many thanks for a comprehensive response. Yes it is Vallejo Model. As you say I will experiment with different ratios of paint to thinner. I had better order some more paint however. Those bottles are tiny!

Thanks again Laurie - I hope eventually to finish this model and get it on display! Need the patience of a saint. I notice that Flory says he has problems with gloss too!

 

[AVB99]

Hello again. I have thre more questions if I may please and, as always, thanks to you experts who share your knowledge and expertise.

1. How long should I wait between applying the Vallejo primer and the Vallejo black gloss paint?

2. Having successfully applied my Vallejo gloss black coats (two of them?), how long should I wait before adding the Vallejo gloss varnish?

3. Is it best to paint brush or air brush the Vallejo gloss varnish?

Regards

Aidan

 

[tecdes]

A lot depends Aidan on the conditions that you leave the paint to cure.

Humid & cold is longer than warm & dry.

But in my garage which is well insulated & quite high on humidity (87% in Jersey 65% average London approx) I leave about 24 hours. Also use sometimes a gardeners incubator which gives perfect conditions & probably 12 hours. This is for matt Vallejo finishes. Gloss I have not used so I cannot answer for that finish. Varnish is the same for matt finishes although it is not the varnish it is the layer the varnish is to be applied to.

Have to say that I sometimes, after all the above, if in a hurry & want to get on I recoat, after the gardener's incubator session, within the hour or less. With matt it dries through both coats. If you watch Flory he dries with the airbrush on air only & gets away with it. Got to watch however the coat thickness or it will separate & you will get cracks with differential drying of the layers. Same I suspect with gloss as the undercoat & gloss may dry at different rates.

Can somebody help on gloss here ? Very interesting topic.

Laurie

 

[AVB99]

Thanks Laurie. I'm happy to wait 24 hours between coats. I'm the most impatient person I know, so this hobby forces me to be more patient.

With regard to the gloss black, I used it today for the first time. It twice clogged my airbrush until I thinned it, again and again with thinners, eventually to about 75%. All a learning curve!

Regards

Aidan