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Hi guys,

Have any of you tried to sand a model very lightly with fine sandpaper before priming to make the paint stick better?
Either metal or plastic models?

I recently had some paint flake of the rim of a plastic base and I figured its because its so smooth. So why not sand it lightly? And maybe even other big smooth areas on the model?

Anybody of you who does this? Or have any experience and can tell if makes any big difference?

Models have fine details. Sanding them would be a bad idea.

Edges of bases? Shouldn't really matter if they're smooth.

What I'd suggest is that your models are probably oily, even greasy fingers leave oils behind. Some models, particularly resin, sometimes need the oils removed from the casting process.

I'd suggest giving the parts / models a quick bath in warm soapy water if you have this problem. And wash your hands before handling the bare plastic.

Then rinse thoroughly in warm/hot water, and then dry the parts off. Easier while the parts are either on sprue or pre-assembled, anyhow.

Primer is made to stick to clean surfaces. Maybe the paint you used wasn't a primer, or maybe a low quality one?

That's likely the cause of the problem. Bases, for example, are probably the part you touch and transfer oils to the most pre-priming.

Sanding, not so much.

Scrubbing with a very fine abrasive: Yes. I use toothpaste to clean any mould release and/or any oxide coating (Most metals will form an oxide coating when exposed to air, it's chemistry. It also stops paint adhering properly) off them before painting. Silver/brass polish can also work.

Not to give them any shine, but to remove the shine and add some "tooth" for the paint.

That's what I am thinking, I wouldn't want to damage the model or change its shape obviously, just give it some microscopic tooth on certain parts that are more exposed when handling. Toothpaste can really do that? Isnt it too soft?

I use veeeeeeery fine grade sandpaper to help get rid of mould lines on plastic models, and do use it to polish up metal models a little. Nothing to help paint stick, but when a white metal model starts to actually look reflective and more metallic it would appear that sandpaper does smooth it down.

My first couple models were like that. Turned out to be oils from fingers. I usually handle them with my bare hands when removing from sprue and cleaning mould lines. When ready to paint I wash the parts and from that point on I wear nitrile gloves to handle the models all the way up till I a seal them with an acrylic sealant.


Automatically Appended Next Post:
My first couple models were like that. Turned out to be oils from fingers. I usually handle them with my bare hands when removing from sprue and cleaning mould lines. When ready to paint I wash the parts and from that point on I wear nitrile gloves to handle the models all the way up till I a seal them with an acrylic sealant. Never occurred since.

If the primer dont stick and the plastic is slick then there are some form of oil on the surface.
Steel wool is finer then sandpaper, more flexible then sandpaper and has soap in it so use that.
but still, use it very, very gently or you will scrub away plastic details.

Yep, paint shouldn't flake off the rim of a base. That's an issue with the surface or the paint.

Washing oils/release agents off first.

That said, I do use 1200 grid sand paper with regard too mould lines and other cosmetics.In addition, I find that a brass wire brush is more useful than a toothbrush when stripping models of old paint. I also use it to scratch up parts that I suspect of being too smooth - mostly this is resin.