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should acrylic paint scratch off with a fingernail


william smith
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Good morning everyone , I had a simple question that has probably been answered hundreds of times , i finally completed my tamiya tiger 1 , it was first sprayed with vallejo white primer , and then vallejo model airs dk panzer grey , ok so bearing in mind this white primer gave a slight rough finish  (because its white) i then painted the panzer dark grey , then it was finished off with 3 coats of gloss , the other day when it was on the shelf i desided to test how durable it was , so i gave it a medium scratch so not too much force , and i noticed tiny speckles of the white primer showing , incredibly small , does that mean my varnish is doing its job?

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As a long term enamel user, I'd say that this is indeed one of the drawbacks of using the water-base acrylics, and is mentioned fairly regularly on this site.  There are of course other acrylics which are not water based, and they apparently are much more durable.

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38 minutes ago, william smith said:

Good morning everyone , I had a simple question that has probably been answered hundreds of times , i finally completed my tamiya tiger 1 , it was first sprayed with vallejo white primer , and then vallejo model airs dk panzer grey , ok so bearing in mind this white primer gave a slight rough finish  (because its white) i then painted the panzer dark grey , then it was finished off with 3 coats of gloss , the other day when it was on the shelf i desided to test how durable it was , so i gave it a medium scratch so not too much force , and i noticed tiny speckles of the white primer showing , incredibly small , does that mean my varnish is doing its job?

Ok ...this is indeed a problem with non solvent based paint ...... like AK, MIG Ammo and so on........... but there is a way around this, i prefer the pigments used in the aforementioned makes but have found the paint to be far to delicate if the recommended primers are used...so to get around this i use Humbrol enamel matt black and white which they do in 50ml tins, this gives a fantastic and very hard base that allows the water based paints too really bite into used this method on my Jagdtiger build and the paint is very durable indeed

 

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15 minutes ago, M3talpig said:

Ok ...this is indeed a problem with non solvent based paint ...... like AK, MIG Ammo and so on........... but there is a way around this, i prefer the pigments used in the aforementioned makes but have found the paint to be far to delicate if the recommended primers are used...so to get around this i use Humbrol enamel matt black and white which they do in 50ml tins, this gives a fantastic and very hard base that allows the water based paints too really bite into used this method on my Jagdtiger build and the paint is very durable indeed

 

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So the issue is the Vallejo model air paint is very fragile? , I should mention the small white specks seem to be the primer as the primer was white 

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1 hour ago, william smith said:

then it was finished off with 3 coats of gloss

 

What gloss did you use? If it was water based then I'd suggest it isn't doing its job. I use gloss and matt coats by Tamiya or Mr Color, either their 'acrylic' or laquer based ones, and I find these to be much tougher than water based ones like Vallejo, which in the past I've found can be rubbed off a finished model pretty easily allowing the underlying paint to be damaged.

 

Keith

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1 minute ago, william smith said:

So the issue is the Vallejo model air paint is very fragile? ,

The Vallejo primer is the reason ...it is not a solvent based paint and so does not bite or key to the plastic it just covers it ....then using the same make of colour over the top means the colour is biting to the primer but the whole lot is not biting into the plastic...... you also said that the primer left a textured finish or slightly rough finish as you put it....it is possible that when you scratched it you broke through the surface colour to the primer and knocked the tops of the rough finish of the primer resulting in the little white spots......... 

My process is as follows

Humbrol matt white and matte black for base primer and pre shade 

Then the chosen colours of choice (in my case AK or MIG)

Then a light gloss coat (again AK or MIG)

Then decals

Then matt coat (again AK or MIG) 

I also when using AK or MIG i use a drying retarder ...this gives the paint time to level into a glass smooth coat (one to two drops per five mils of colour)

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1 hour ago, keefr22 said:

 

What gloss did you use? If it was water based then I'd suggest it isn't doing its job. I use gloss and matt coats by Tamiya or Mr Color, either their 'acrylic' or laquer based ones, and I find these to be much tougher than water based ones like Vallejo, which in the past I've found can be rubbed off a finished model pretty easily allowing the underlying paint to be damaged.

 

Keith

I use humbrols gloss varnish spray

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1 hour ago, william smith said:

I use humbrols gloss varnish spray

Couple of problems there too.....while weathering and using solvent based weathering products will be fine (because you use them sparingly) coating over the top of water based acrylic with a solvent based lacquer is almost certainly going to soften the paint underneath.....also a possible problem is how much paint was used and the amount of layers....with solvent based just a few hours and everything hardens off but acrylic needs to be laid in thin coats until the desired colour is achieved then left too dry for at least 12 hours before pushing on with the finishing coats and weathering...it is possible that on top of using a solvent based gloss you may not have left the underlying colour time to dry ...the coat of gloss is now preventing those colour coats from drying because you have essentially barrier coated them from the air.

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2 hours ago, M3talpig said:

coating over the top of water based acrylic with a solvent based lacquer is almost certainly going to soften the paint underneath.....

 

You're right, that's true when using a spray can, forgot that. I have used laquer based clears over water based acrylics, but only in very light mist coats using an airbrush at low pressure....

 

Keith

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This is an age old problem and one which the auto industry has been dealing with as the use of plastic trims and body components has been steadily increased

 

I have been experimenting with using an adhesion promoter in order to get acrylics to better adhere to the plastics commonly found in our kits. The product  have been using is marketed by Dupi Color, at least in North America - I couldn't say if they available overseas but in any case there will be similar products available. 

 

Specifically, this is the one I have been using:  https://www.duplicolor.com/product/adhesion-promoter/

 

and for more information on adhesion promoters, how they work, and why they are used: https://www.google.com/search?q=how+does+paint+adhesion+promoter+work&rlz

 

This is the result of a recent test:

p?i=5c239b85dc0ad4daa307c803fb559846

 

The white cards are a laminated plastic coated card stock. The plastic with which they are laminated is not styrene but similar. I use these cards to make colour patches when I am mixing and matching colours and the hobby acrylic paints do not adhere very well. The top card is uncoated and the bottom card was treated with the adhesion promoter. The test was to use my calibrated thumbnail and do a simple scratch test - uncoated, obviously easily scratched off but on the coated card the paint remained well adhered. The paints used for this test were Tamiya X-xx and XF-xx acrylics.

 

Tamiya makes a metal primer as does Mr. Metal Primer-R which are marketed for use on metal ( i.e. photo etch ) I have found they work similarly to the Dupli Color adhesion promoter but I am still testing these. These are available in spray cans or a brush on liquid.

 

Has been working for me, your mileage may vary.

 

cheers, Graham

 

 

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15 minutes ago, GrahamCC said:

The white cards are a laminated plastic coated card stock. The plastic with which they are laminated is not styrene but similar. I use these cards to make colour patches when I am mixing and matching colours and the hobby acrylic paints do not adhere very well. The top card is uncoated and the bottom card was treated with the adhesion promoter. The test was to use my calibrated thumbnail and do a simple scratch test - uncoated, obviously easily scratched off but on the coated card the paint remained well adhered. The paints used for this test were Tamiya X-xx and XF-xx acrylics.

 

Tamiya makes a metal primer as does Mr. Metal Primer-R which are marketed for use on metal ( i.e. photo etch ) I have found they work similarly to the Dupli Color adhesion promoter but I am still testing these. These are available in spray cans or a brush on liquid.

 

Has been working for me, your mileage may vary.

 

cheers, Graham

 

Thanks for this Graham.....will look into this further and have a play to see how it works with water based acrylic like AK and MIG ....we used adhesion promoters in the auto industry when we were phasing out cellulose paints and moving to more modern and less dangerous options ....never gave it a thought for model making ....good call :thumbsup:

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@M3talpig another solution for a good water soluble primer is Stynylrez primer ....the Mig one shot primer is of the same make and it really is a tough selfleveling primer!
I even use it to make a good primercoat for enamels and it levels perfectly flat👍

And they have sixteen different base colors😁
Untill now I still didn’t experienced any paintlifting or specs as you describe..

 

cheers, Jan
 

 

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I used to use hycote black primer that you can get from places like the range in the UK. 

 

Since getting the airbrush though I have been using vallejo mecha primer and not had any issues just give a couple hours to dry then it's fine. 

 

Might just be me though lol

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My priming/painting angle of attack that I have been quite lucky with is  -  Tamiya Rattle can surface primer  left a  few good days to de gas,  then if the finish is ok  a couple of  light spray overs again using the Tamiya Rattle cans  in my colour of choice,  then again put away  but thiis time  for longer (in my case about a week)  then any  detailing - shading/washes and highlighting can be one using Acrylics.

And I will seal it all after a week or so using Tamiya's  Flat Laquare  cans, as long as the Acrylic is Fully dried  the laquare is fine to be sprayed over.

 

I intend to take this route with my Chally build here.

 

Erk.

Edited by ERK
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Halford's acrylic primer works for me.

Had a ship model painted with this and Vallejo paint on it for over a year between camouflage coats. Got moved around and abused over a Christmas period and the Vallejo stayed pristine even under the masking tape.

Tom

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5 hours ago, Bozothenutter said:

Another vote for automotive 'adhesion-promotor' or 'etch primer' but the do bring other problems in the H&S department.

 

'etch primer' also known as self etching primer contains an acid the purpose of which is to 'etch' the metal onto which it is applied in order to promote better adhesion of the coating.

 

Etch primers could be used on plastic but there is no advantage adhesion wise as the acid which they contain will not etch the plastic.

 

cheers, Graham

 

 

 

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The more layers, the less detail remains. Less detail means worse view.

I do not use any primer, I paint my models with Tamiya XF acrylic paint. I often use chipping technology, which means I rub the paint ruthlessly, and I’ve never damaged a layer of paint before.

If an angry neighbor walks over the side of a vehicle with a sharp nail, no primer will save, so I keep my models on the shelf :rofl:

 

Vytautas

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I contact Mr Hobby about their Mr Metal Primer-R.  This product is NOT an etching primer and from their brief description is more akin to an adhesion promoter. 

 

Also, Vantage Modeling Solutions ( aka: VMS ) have a metal prep/primer adhesion promoter product described as a paint adhesion enhancing agent.

 

https://www.vms-supplies.com/vms-metal-prep-primer

 

cheers, Graham

 

 

 

 

 

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On 12/02/2021 at 16:45, janneman36 said:

@M3talpig another solution for a good water soluble primer is Stynylrez primer ....the Mig one shot primer is of the same make and it really is a tough selfleveling primer!
I even use it to make a good primercoat for enamels and it levels perfectly flat👍

And they have sixteen different base colors😁
Untill now I still didn’t experienced any paintlifting or specs as you describe..

 

cheers, Jan
 

 

 

I tried Stynylrez and hated it.... same problem with poor adhesion.   I went back to Halfords/Simoniz/Hycote whatever automotive primer.

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I started using Citadel/Warhammer Chaos Black rattle can primer years ago after using it on - unsurprisingly - Warhammer models for my son.  It now comes in other colours including white, grey, green and sand and a couple of metallics.  Wharever it is, it's good.  It doesn't smell like an enamel but it isn resistant to acrylic paint removers.  It seems to bind well to plastic.

 

Lately I've switched to the equivalent product from Army Painter but in a dark brown, as that better represents armour colour should the top coats wear or scratch theough in handling.  It seems to perform just as well as the Citadel product.

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2 hours ago, Six97s said:

 

I tried Stynylrez and hated it.... same problem with poor adhesion.   I went back to Halfords/Simoniz/Hycote whatever automotive primer.

Had it twice and that was when I degreased my model with IPA but after using white spirit to clean my model everything went very well..

Very dry layering during applications doesn’t work either in my book....but hey those are my experiences and it works for me😉

 

cheers, Jan

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I use Vallejo and Mig and not had this problem. 

 

I use Humbrol rattle can as a primer. 

 

Clear coat which I know that some have problems with is Humbrol rattle can. 

 

I don't get chip problems. It's rock solid. 

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