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is primer chemically different from flat grey?


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Cant speak for others... but I sure as hell do.    

 

I black base, and I have two different primers.  Mr.Surfacer 1500, and AlcladII gloss black primer.   The only other "black" that I have is model masters water based black that I use for brush painting details.  I'll leave the bare Mr.Surfacer if the needed color is a more washed out black... and if I need it really black (like anti flash paint or ejection seats), I'll use the Alclad II gloss black.   

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On 12/23/2019 at 11:10 PM, DarkKnight said:

is it chemically different, Ive alway heard spray primcer on so paint sticks to the primer, but is it chemically different from any flat color? if so why do most aircraft builders and amrmor builders not use it?

 

Good question. In my personal estimation, I would guess that many of them are simply grey paint. Some, like Tamiya's fine or  Mr Surfacer probably have finer quality and maybe better adhesion.  I don't prime as  I don't see a need for it, and it's just extra layers of paint build-up. In areas that have had major modification work, I'll cover it with a few good coats, but I'll usually use the specific color it is anyway.  I do like to have an enamel or lacquer base before I use acrylics, but I don't always do this either.  If I'm low on top color (as I probably will be in the future with my Testors supply) I'll use a primer so I can finish will a thin top coat.

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I prime so that I have a consistent background color and to highlight any surface problems that still need correction. I find the former especially useful when using some of the very thin lacquers like MRP. While generally good in coverage, the consistent background eliminates any strange changes in color due to differences in the colors on an unprimed kit (from filling with putty, aftermarket parts, etc).

As far as question of primers being different from regular paint, some primers have coarser pigments (Mr Surfacer) to cover and fill in small scratches. Also, I'm pretty sure the primers designed for metal and resin by Gunze are a different composition. In fact, their metal primer is a clear product, designed solely to provide a surface that paint will adhere to.

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Not really sure what you are talking about.
I would imagine at least 90% of modellers of any subject use a primer.

 

Some primers are chemically very different to paint. I have aerosol etch primer that once sprayed on will "eat" into the surface of the model to make sure it sticks to it ensuring it is activated and ready for another paint over the top.

 

Could I then leave that surface as the colour serface that I want as the final finish...  Well yes there is nothing to stop me but grey is rarely the colour I want to end with. Its also the outside surface of a primer, it will in general leave a rougher surface than a paint would. Not always of course, some primers leave a surface equal to paint but generally a primer will be rougher.

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On 12/24/2019 at 6:10 AM, DarkKnight said:

is it chemically different, Ive alway heard spray primcer on so paint sticks to the primer, but is it chemically different from any flat color? if so why do most aircraft builders and amrmor builders not use it?

 

This is not an answer to your question, but I found the following an interesting experience.

 

In our club we built more or less identical resin models. I was the first to notice that paint adhesion was a real problem, everything got scratched very easily. We all tried various paints (enamel, waterbased acrylic, lacquer acrylic, Mr Surfacer) and nothing worked. In the end I found out that a *throroughly* dried enamel would stick properly. I'm talking 4-5 days of curing, or a forced heat cure. That was the solution that everyone used, then continuing with their paint of choice.

 

For me it was the first time that I needed a paint with mostly adhesion qualities (call it a primer) before the 'colored' paint could be used.

 

Rob

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1 hour ago, Rob de Bie said:

 

This is not an answer to your question, but I found the following an interesting experience.

 

In our club we built more or less identical resin models. I was the first to notice that paint adhesion was a real problem, everything got scratched very easily. We all tried various paints (enamel, waterbased acrylic, lacquer acrylic, Mr Surfacer) and nothing worked. In the end I found out that a *throroughly* dried enamel would stick properly. I'm talking 4-5 days of curing, or a forced heat cure. That was the solution that everyone used, then continuing with their paint of choice.

 

For me it was the first time that I needed a paint with mostly adhesion qualities (call it a primer) before the 'colored' paint could be used.

 

Rob

 

Yeah...
you see Resin, be it epoxy, vinylester, polyester or what ever has properties all of its own that prevent paint from sticking to it. Plastic is a different medium and while at first glace the problem is the same (the paint wont stick) the reasons why is or can be different and the solution to one isnt always the best solution to the other.

 

Can I ask, in your resin models what is the resin used? for instance is it an epoxy casting resin?

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11 hours ago, ElectroSoldier said:

 

Yeah...
you see Resin, be it epoxy, vinylester, polyester or what ever has properties all of its own that prevent paint from sticking to it. Plastic is a different medium and while at first glace the problem is the same (the paint wont stick) the reasons why is or can be different and the solution to one isnt always the best solution to the other.

 

Can I ask, in your resin models what is the resin used? for instance is it an epoxy casting resin?

 

It was regular polyurethane resin, the caramel-colored kind. Is epoxy more difficult, in general? I did some epoxy resin casting 20+ years ago, but I don't think I ever painted those parts.

 

Rob

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Im trying to think of how to explain this without getting to technical.

 

This is a really simple version.

As PU cures an oil forms on the outer surface of it, it needs to be activated in order to get something to bond to it, be that a primer or paint or another resin...

 

It really depends on the spercific resin as to the best way to activate its surface, the manufacturer would be able to offer more help than I can about spercific resins though, I dont use them all, just some of them.

 

Difficult?

Im not sure if any resin is difficult... I mean control and safety measures need to be taken with any of them. I prefer a PU casting resin for model parts myself, but there are situations where I prefer an epoxy based system and then sometimes polyester or vinylester, it depends on what Im making.

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On 12/24/2019 at 6:10 AM, DarkKnight said:

is it chemically different, Ive alway heard spray primcer on so paint sticks to the primer, but is it chemically different from any flat color? if so why do most aircraft builders and amrmor builders not use it?

Primer (for plastic kit modelling") "etches" plastic to improve adherence.

Normally, the finer pigments and elements in a paint, the better the paint is.

Primer are designed in the opposite trend, their elements and grains are bigger to fill gaps on the kit´s surface.

 

Armor builders tend to not use primer, bc they don´t care about surface roughness.

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11 hours ago, ElectroSoldier said:

Im trying to think of how to explain this without getting to technical.

 

This is a really simple version.

As PU cures an oil forms on the outer surface of it, it needs to be activated in order to get something to bond to it, be that a primer or paint or another resin...

 

It really depends on the spercific resin as to the best way to activate its surface, the manufacturer would be able to offer more help than I can about spercific resins though, I dont use them all, just some of them.

 

Very interesting!! I would love to hear more, even if it's generic. I never experienced paint adhesion problems on resin parts before, so this 'incident' was quite an eye-opener. I always suspected that silicone oil from the mold would create most of the paint adhesion problems, so your comments are intriguing..

 

Rob

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1 hour ago, Rob de Bie said:

 

Very interesting!! I would love to hear more, even if it's generic. I never experienced paint adhesion problems on resin parts before, so this 'incident' was quite an eye-opener. I always suspected that silicone oil from the mold would create most of the paint adhesion problems, so your comments are intriguing..

 

Rob

 

It really depends on how you make it what it will be used for.

Most of the time resins are case in what i would call a prototype environment... Even if you consider it a mass production environment its really not.

A release agent should be applied in order to allow it to release it easier from the tool, it sticks to the parts being produced too, and that needs to be removed too as it is designed to stop things from sticking together, but in the case of release agent its to stop the part sticking to the tool, 

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I've got some Testors Model Master primer, it appears to be a cross between flat and gloss paint. I use it for small areas that I brush on.  I have also used it for radomes and antennas on Vipers without painting over.

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You guys do realise that a primer and what counts as a primer very much depends not only on the substrate you are painting (ie plastic in some form, resin, metal) but also on the paint you intend on putting over the top of it.

 

It doesnt have to have a matt finish in order to be a primer.

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