Recommended Primers for PLA

[BigJimSlade]

Does anyone have any primer recommendations for PLA? (any not to use?)

I am doing ship modeling. 1:350. Have build my own parts. I need to get rid of the line patterns. The lines are small enough that it looks like some kind of primer would do the work for me.

[jsc]

I've successfully used a high build sandable automotive spray primer in the past. Rustoleum brand, but that's just what I found on the shelves, so I can't really recommend it over other brands. jimc does a lot of this sort of thing, so maybe he would have some brand recommendations worth listening to.

There's also a thread in the how-to forum I started with links to a clear epoxy that's intended for 3D printing, you may want to check that out. Although, as jimc points out in that thread, if you're going to paint, it would be better to stick to primer. If you want a metallic look, though, it might be worth trying.

[jimc]

if you are limited to rattle cans then the primer jin mentioned will work just fine. if you have a compressor and a small spray gun then by all means you should use an automotive urethane primer. its 2 component and will need a catalyst. its very easy to come by. since its not just air dry or lacquer base like rattle can stuff it will bond much better to pla and shrink less into the layer marks. you can get the rattle can stuff or a cheaper urethane primer at almost every napa. napa usually carries enough autbody supplies to get by with a small project.

[BigJimSlade]

I have an airbrush (very small spray gun). Would that work for a urethane primer?

[jimc]

No, primer is really thick so it builds up easy and can be sanded smooth. You could reduce it down so its thinner but with an airbrush you going to be limited to very tiny parts. A cheap small spray gun is all you would need

[jsc]

So, I have occasion to prime/paint another model. I just happened to watch Adam Savage build a replica Barbarella rifle, and noted that he made liberal use of a hair dryer to quicken the drying process, with a warning that too much heat would burn the paint. I would really like to minimize the time between coats, how much can I push it? I tried it on a sacrificial part and it seems like I can get a dry looking part within a few minutes, but trying to sand it revealed that it was still quite soft and easy to damage. What is the minimum time between coats, and between priming and painting?

[jdacal]

I've also been trying to find a primer that will cover the layer marks on PLA. I need something that doesn't smell to high heaven even if it means airbrushing 50 layers on it. I live in an apartment complex and can't stink out the neighbors. Plus my wife is asthmatic and allergic. Talk about walking a thin red line...

[jimc]

jin, you can force dry paint but you cant go too fast with it either. you have to remember that there are solvents in paint that needs to flash off. once all the solvents are out then its dry. the problem is and what you dont want to do is get it too hot because that will skin over the outer layer of the paint leaving the solvents in the paint film trapped then the heat causes the solvent to flash anyway making air bubbles in the paint film. technical term for this is called solvent pop. the ideal situation is to put on a thin coat then just warm the paint so it flashes off, apply another thin coat, heat and so on.... this will avoid trapped solvents. you really dont want to get it hot anyway since you pla is going to just turn to rubber.

as for the primer, all of them except a waterborne primer is going to stink a little. not much you can do. waterborne primer is ok but its really made specifically for rubber bumpers on your car. im not sure if its avail on rattle cans either. its terrible to sand and just balls up on sandpaper. really not the idea stuff to use. for you guys without any spray equipment or living in apartments i would stick with this...http://www.semproducts.com/automotive-p ... r-surfacer they are a good company that makes decent stuff. its not a good catalyzed primer BUT its not bad and probably the best thing you guys could use that comes out of a can. lightly sand the bulk of your layer marks out of the pla with some 220 then do 3-4 coats of this stuff, sand again, reapply a couple more coats, finish sand with 400 grit and it will be ready for paint.

[jdacal]

Thanks Jim!

I had ordered this but haven't had a chance to try it yet. Have you ever tried it? Says it should be ok with a .5 airbrush needle. For smaller prints I suppose.

http://www.amazon.com/gp/product/B00K3K ... UTF8&psc=1

[jimc]

Hmmm no i never used that stuff so i dont really have any feedback on it.