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Hey all, I have seen little snippets here and there about the possibility of magnets affecting airbrush work. Well, I was looking for more detailed input on this. I've got a fully magnetized GK army (about half are the metals from the previously released models, and the other half the new plastics), and I wanted to airbrush as much as possible in this army. What can I expect? Thanks!

kanebbcksc wrote:
Hey all, I have seen little snippets here and there about the possibility of magnets affecting airbrush work. Well, I was looking for more detailed input on this. I've got a fully magnetized GK army (about half are the metals from the previously released models, and the other half the new plastics), and I wanted to airbrush as much as possible in this army. What can I expect? Thanks!

You can expect thin layers of paint on top of the magnets... I'm curious now, what have you heard about magnets affecting airbrush work?

The magnets won't affect the airbrushing in the least.

As with all models that have embedded magnets in them, if the paint is directly atop the metal, and touching another magnet with paint atop it, the paint will wear off fairly quickly.This may be accelerated by the thinner coats an airbrush lays down.

Forget where I read it, but it said that the magnets can cause some weird "swirls" in the flow from the airbrush when it nears the magnet itself or something like that. Something to do with the magnetic field and the atomization of the paint. Sounded kinda weird to me, but who am I to discount it. I'm no expert on magnets or airbrushing by any means. As far as paint scraping off from contact between the magnets, I was hoping a good layer of varnish would help protect against that!

I don't think the fields from those magnets are sufficient to affect whatever elements of the pigment that would normally be susceptible to them.

So far as varnish, it will help, depending on how much traffic that join is going to take. You may wish to use untinted polyurethane floor polish to seal those areas, it's very hard and quite tough - you'll need to dullcote over it, though, it's shiny.

I'm a very amateur airbrusher, I've been using it primarily to lay down base-coats or do large patches of different colors. My models are riddled with magnets, 4x 1/8"s minimum in a space marine and sometimes twice that after weapons and or heads and packs. I haven't noticed anything at all, but again its all been pretty simple stuff.

The only magnets I ever see showing are the ones for optional attachments that are sometimes left off.. It may be possible a super thin (maybe even liquid gs) coat of greenstuff would create a surface the paint is less likely to rub off of without negatively affecting your magnets?

Only if youre using metallic paints based on ferrous pigments (or for that matter paints based on magnetic pigments). It mightbe an issue with cetain colors from certain ranges but i wouldnt worry much.

I actually keep a big magnet on my desk just to double check paints and what not for magnetic materials. There are not too many hobby paints which have pigments that are affected by it, but some art paints do.

When you airbrush with them, you get funny things over magnets - the field bands cause the paint to veer off in different directions, and sometimes you get growths of the paint piling up on top of itself.

Normally it isn't metallic paints that will be problematic (the "metal" flakes tend to be minerals like mica as opposed to actual metals). Artist paints and higher end airbrush paints can be problematic - they tend to use traditional colors like Burnt Sienna (Calcinized Iron Oxide), Umbers (Iron Oxide containing Manganese), Cobalts (cobalt - obviously) and Ochres (Hydrated Iron Oxide). There are likely more as well - but those are the ones which I use with some frequency and I know are magnetic.

The first time I noticed it was when I was weathering a model with a wash made from burnt umber oil paints being sprayed through an airbrush. The stream was pulled towards the magnet...sort of like you can bend water with a statically charged comb. When it was on the model - there was a fair amount of pooling around the magnets.

Over the years - other paints have behaved in other ways.

Sean_OBrien, that's what I was concerned about... I've got a large collection of Vallejo Game Colors, and the Minitaire paint set. We'll have to experiment a bit and see what happens I guess. Not sure if either of those brands would be considered "Artist" paint (don't really think so personally). Well, guess I'll find out when I redeploy in a few months and hunker down and get some stuff painted up!

No - most Vallejo use synthetic pigments like other hobby paint brands. It is in order to meet the child safe certifications that they shoot for (ASTM something or other...I don't have a bottle of paint in front of me - but it is on most of their labels).

Some model paints do use metallic pigments though, as they are shooting at a different demographic (especially when you are looking at lacquers and enamels). The fine-art line of Vallejo paints likely still use metallic pigments...

http://www.acrylicosvallejo.com/en_US/premium-airbrush-color/family/6

Though, I haven't gotten around to trying any of those out to know for certain. They use traditional color names on those, and generally speaking if they use a traditional name...they will use traditional pigments as well (just in a new base with a finer grind).

solution is to smooth it down after drying if it appears ..and then apply a wash after the smoothing ..blends it all in nicely ..

a magnet would only affect and airbrushes spray pattern if the particles of paint were charged, as far as I know the spray is only charged when painting cars to ensure an even coat, so it shouldn't happen with airbrushing a model (and I thought i'd never use that part of my GCSE physics again...)

The spray would be charged when doing powder coating, where the dry paint particles are charged oppositely to the job, minimising wastage and ensuring a really nice even coat.
Ive not heard of any wet paint being charged, perhaps a pigment could be magnetic but it would only occur with paints containing that pigment.

As for the miniatures, I airbrush and use magnets, and never encountered this yet (or the effect is incredibly subtle and I can't see it)
I've sprayed many citadel colours thinned out, many craft acrylics, artists inks, cellulose and 2pack car paints and none of those gets this happening.
I wouldnt worry about it, what you say makes sense to me but only if the paint is charged or magnetic in its own right which would probably be a bit odd.

 macc92 wrote:
a magnet would only affect and airbrushes spray pattern if the particles of paint were charged, as far as I know the spray is only charged when painting cars to ensure an even coat, so it shouldn't happen with airbrushing a model (and I thought i'd never use that part of my GCSE physics again...)

I would go back to my text books then...

The issue with powder coating are the charges of the paint and the substrate. Charges though are pretty easy to build up, and exist in a lot of stuff we use all the time. Water molecules in particular are highly charged and easily influenced by static charges (again - go back to that grade school science experiment of bending water with a static charged comb). Moving air tends to generate its own charge as well, though the charge develops in the path which the air is moving through (your airbrush). Static ends up being an issue, because plastic builds a charge quite easily, though more often than not...the issue between static and plastics isn't any particular interaction with paint, rather that it will end up sucking in dust like a vacuum that can end up ruining an otherwise excellent paint job. You can notice banding effects when you are doing very, very thin passes with an airbrush though these usually clear up by the time you have achieved full coverage...though if you are doing very fine glazes over large areas - it can be your bane.

As Hairy mentions, the reason isn't so much to get an even coat (though it does produce nice smooth coats) rather an issue of economy. You spray the powder onto the charged substrate and then the object is moved into a giant oven. The oven melts the powder and it forms the candy coat of the M&M, while any powder which did not stick to the substrate when it was sprayed on can be collected and reused.

The issue with magnets are related to ferromagnetic pigments. In that case, the materials like iron oxides, cobalts, nickels and other metallic compounds are used as pigments in the paints. These materials end up having a structure that is impacted by magnetic fields in a noticeable manner. The effect will depend on the pigment, its concentration and the strength of the magnetic field. Cosmetic manufacturers have used these traits to develop certain nail polishes that are impacted by special magnets that are used over top of the polish before it has dried (and nail polish is only half a step removed from miniature paint).

My MSc dissertation was on nanomagnetic particles and what Sean says is pretty much correct. The action of the paint particles moving through the airbrush, air, etc will impart a charge upon them which will allow them to be affected by magnetic fields (via the Lorentz force). The effect will not be huge for most generic artistic applications though and any banding/etc will probably mostly be from the interactions of the static charges.

It is an effect used in many micro/nano scale applications.

The force to generate this banding effect would have to be quite strong. It not only needs to affect the pigment particles, but needs to affect them with enough force to push or pull the acrylic binder/medium that the pigment is suspended within(which is the vast majority of the paint).
The done thing in the paint spraying industry is to use 'anti static panel wipe' before any application of paint to a job, say a car for example.
This would all but eliminate any of the banding issues related to static build up, but not the field of the magnet questioned in the op.