Another paint issue.

[Donny]

Looks like SMS paint doesn't like Vallejo white primer. painted a body today, Vallejo white primer and SMS pearl jade green and I have crazing. Applied as instructed, light coats over white primer for the pearl effect. I have not used SMS paint before, so guessing I'm doing something wrong or just inexperience with air brushing.  Most of the body looks okay, it's mainly the left sill. It's supposed to be a "pearl" effect/finish, but to me it looks very metallic, soon as I get a minute, I'll post some pics, right now my wife has me moving furniture, she's rearranging the house. (bah!) 😡

Don    

[johnyrotten]

I'm not familiar with sms paints, looking them up they say they're an acrylic lacquer. It could be the primer isn't compatible with the paint, as Vallejo is a "true" acrylic. Here's a link to a "cheat sheet" to help avoid these kinds of problems. Hopefully this helps you out.👍👍

 

https://www.airbrushmodeler.com/model-paint-compatibility-chart/

[stitchdup]

i've not used either of those paints but how long are you leaving it between primer and paint?

[ColonelKrypton]

4 hours ago, johnyrotten said:

as Vallejo is a "true" acrylic

That is a really a misnomer.

As most are aware, a paint or coating is comprised of three basic ingredients - pigment, that stuff which gives the paint it's colour, binder or carrier - that stuff which makes the paint or coating a paint or coating, and solvents - that stuff which keeps the paint liquid and ready to use.

Acrylic paints use an acrylic resin as it's binder or carrier. An acrylic resin can be formulated to use a hydrocarbon carrier OR a water based carrier.

Vallejo, AK Interactive, Citadel, Army Painter, common craft store acrylics use an acrylic resin having a water based carrier, hence water based acrylic.

Tamiya Acrylics, SMS paints, Mr Hobby Aqueous, use and acrylic resin having a non water based carrier, hence often referred to as acrylic lacquers which is also a misnomer.

Incidentally, the solvents used in non-water based acrylic paints are organic solvents, that is they contain carbon. Water is a non organic solvent as it does not contain carbon.

I did a quick search for the safety data sheets (SDS) for the SMS paints and found these at https://www.scalemodeller.com.au/pages/msds

thinner: https://cdn.shopify.com/s/files/1/0039/5565/4765/files/Acrylic_Thinner_MSDS_1.pdf

paint: https://cdn.shopify.com/s/files/1/0039/5565/4765/files/ACRYLIC_LACQUER_SDS_3402_v1.pdf

 

These paints, based on the chemical ingredients listed in their SDS show that they are more like what we might consider a lacquer in that they contain solvents like tolene, naphtha, acetone, and ethanol.  The SDS for the paints show that it also contains a small bit of methyl ethyl ketone ( MEK ).

It is not surprising that Don encountered some issues. 

To be fair, water based acrylics like Vallejo do dry very quickly but even when dry to the touch they are not fully cured and require at least 24 hours and in some cases even longer before they reach the point of being fully cured. 

I have in the past been able to apply non water based acrylic ( i.e. clear coats ) over water based acrylics with no ill effects but only after a sufficient period of time to allow the water based acrylic to fully cure. As a matter of course, I always let any water based acrylics cure for two days. However, I have no first hand experience using SMS paints.

Here is a very interesting Youtube video in which the author goes into some detail about acrylic paints and is well worth the half hour spent watching:

 

cheers, Graham

 

 

[johnyrotten]

29 minutes ago, ColonelKrypton said:

That is a really a misnomer.

The reason true is in quotation marks. Paint terms get thrown around all willy-nilly and lead to confusion. Once someone knows what plays well with what, it's not so much of an issue. And a very good point about the dry vs cured. Yet another point where issues pop up.

[Dave G.]

From what I've read about the SMS paints the solvents in them are fairly hot. You're going to want a lacquer primer under those paints. Or that's what I would use anyway. Otherwise you could  get crazing, cracking or sand scratch swelling going on. It's been a couple of years now since I've shot lacquer color but I keep Mr Primer Surfacer 1000 ( in a jar) on hand and also a Mr Surfacer spray can on hand for lacquers, in case that desire for lacquer re-ignites.

[Radretireddad]

I’ve tried Vallejo acrylic primer and found it wouldn’t stick to bare plastic at all. You’ll need a primer that’s compatible with the paint you’ve chosen.

[johnyrotten]

27 minutes ago, Radretireddad said:

I’ve tried Vallejo acrylic primer and found it wouldn’t stick to bare plastic at all.

I've read the same. Decided against it from the start. Always hear "paint is only as good as what's underneath it."

[Donny]

12 hours ago, johnyrotten said:

I'm not familiar with sms paints, looking them up they say they're an acrylic lacquer. It could be the primer isn't compatible with the paint, as Vallejo is a "true" acrylic. Here's a link to a "cheat sheet" to help avoid these kinds of problems. Hopefully this helps you out.👍👍

 

https://www.airbrushmodeler.com/model-paint-compatibility-chart/

Just read that article John, very informative - thank you. I'll read the subs sometime today, hopefully, if my wife doesn't have me moving more furniture. I have been using mainly Tamiya paints, but saw an article about SMS and spray from the jar ready thinned and thought I'd give it a shot. Opened another tin of worms.🙄

Don

[Donny]

11 hours ago, stitchdup said:

i've not used either of those paints but how long are you leaving it between primer and paint?

Two days Les. I found  the Vallejo primer very soft at first, so put it in the oven for three hours and then let it sit for the rest of time, all up about two days.

Don

[Donny]

7 hours ago, ColonelKrypton said:

That is a really a misnomer.

As most are aware, a paint or coating is comprised of three basic ingredients - pigment, that stuff which gives the paint it's colour, binder or carrier - that stuff which makes the paint or coating a paint or coating, and solvents - that stuff which keeps the paint liquid and ready to use.

Acrylic paints use an acrylic resin as it's binder or carrier. An acrylic resin can be formulated to use a hydrocarbon carrier OR a water based carrier.

Vallejo, AK Interactive, Citadel, Army Painter, common craft store acrylics use an acrylic resin having a water based carrier, hence water based acrylic.

Tamiya Acrylics, SMS paints, Mr Hobby Aqueous, use and acrylic resin having a non water based carrier, hence often referred to as acrylic lacquers which is also a misnomer.

Incidentally, the solvents used in non-water based acrylic paints are organic solvents, that is they contain carbon. Water is a non organic solvent as it does not contain carbon.

I did a quick search for the safety data sheets (SDS) for the SMS paints and found these at https://www.scalemodeller.com.au/pages/msds

thinner: https://cdn.shopify.com/s/files/1/0039/5565/4765/files/Acrylic_Thinner_MSDS_1.pdf

paint: https://cdn.shopify.com/s/files/1/0039/5565/4765/files/ACRYLIC_LACQUER_SDS_3402_v1.pdf

 

These paints, based on the chemical ingredients listed in their SDS show that they are more like what we might consider a lacquer in that they contain solvents like tolene, naphtha, acetone, and ethanol.  The SDS for the paints show that it also contains a small bit of methyl ethyl ketone ( MEK ).

It is not surprising that Don encountered some issues. 

To be fair, water based acrylics like Vallejo do dry very quickly but even when dry to the touch they are not fully cured and require at least 24 hours and in some cases even longer before they reach the point of being fully cured. 

I have in the past been able to apply non water based acrylic ( i.e. clear coats ) over water based acrylics with no ill effects but only after a sufficient period of time to allow the water based acrylic to fully cure. As a matter of course, I always let any water based acrylics cure for two days. However, I have no first hand experience using SMS paints.

Here is a very interesting Youtube video in which the author goes into some detail about acrylic paints and is well worth the half hour spent watching:

 

cheers, Graham

 

 

Thanks Graham, lots of info I didn't have or know. (Back to chemistry classes). I'll follow up on all those referrals, thank you. I've found Paint to be my biggest issue since returning to modelling.

Don

[johnyrotten]

2 minutes ago, Donny said:

I've found Paint to be my biggest issue since returning to modelling

I think a solid 90% of issues are paint related in the hobby. Everything else is "nuts and bolts" as I say. Paint is chemistry,whole different animal. Good luck with your build, and be careful moving any furniture. 

[Donny]

2 minutes ago, johnyrotten said:

I think a solid 90% of issues are paint related in the hobby. Everything else is "nuts and bolts" as I say. Paint is chemistry,whole different animal. Good luck with your build, and be careful moving any furniture. 

Thanks John, have to agree, it's a really technical/in depth subject. I've taken the body back to the base and will start fresh with the paint. I have SMS primer (arriving today), so will see how that works out, their paint their primer, hopefully should work. The furniture, had to cut out a piece of carpet, slipped with the knife, now have a nice slice in my big toe. 😡 Least it will give me a break, back to modelling.😁

Don

[Donny]

5 hours ago, Dave G. said:

From what I've read about the SMS paints the solvents in them are fairly hot. You're going to want a lacquer primer under those paints. Or that's what I would use anyway. Otherwise you could  get crazing, cracking or sand scratch swelling going on. It's been a couple of years now since I've shot lacquer color but I keep Mr Primer Surfacer 1000 ( in a jar) on hand and also a Mr Surfacer spray can on hand for lacquers, in case that desire for lacquer re-ignites.

HI Dave, do you find the Mr Primer Surfacer 1000 works okay with most paints?

Don

[peteski]

Back 30 or 40 years ago most modelers used enamel paints formulated  for models (plastic safe).  Now there are dozens of brands (with all sorts of chemistries) which are sold for painting plastic models. Mixing brands or even chemistries often results in incompatibility, resulting in ruined paint job.  Often touted recommendation on the forums is that wherever you try some new painting method or paint combination, a test should be made on some unimportant plastic item (like a polystyrene disposable spoon) to make sure there are no adverse reactions.

And as johnyrotten mentioned, the paint terminology that has crept into the modeling world is often inaccurate and vague.  I cringe when modelers use blanket statements as "acrylics" to describe a wide range of paints with different chemistries. There is unfortunately no easy fix for that, but understanding the basics of paint chemistry makes us better modelers.

[OldNYJim]

I’ve said it before and I’ll say it again…I don’t know why the people mixing these paints for use on styrene won’t use a solvent that isn’t as aggressive as the solvent for regular automotive paint.  

Less volatile solvents and reducers exist, the place I work uses them regularly for surfaces MUCH more delicate than styrene…seems like a lot of model paint companies just uses a standard solvent that really isn’t suitable for modern kit plastic.  Not sure why…cost?

I know a LOT of people get these to work ok…but it could be so much easier and make for a better product if you didn’t have to be quite so cautious with them all