Prime or not to Prime?

I prime the surfaces when:

1) I have done a bunch of filling and need to see if the seams are properly filled and smoothed. The primer eliminates the contrast between the filler and the plastic so it is easy to tell if the filling was done properly.

2) I'm spraying acrylic and intend to mask the area. Enamel or laquer primer adheres to the surface better than acrylics, and acrylics adhere better to them than bare styrene.

Other than that I don't usually prime parts. I do use the Tamiya Fine Surface Primer and have been quite happy with it except on metal parts. There are some others that are supposed to be good to though, such as Floquil, but I haven't tried them.

I always prime with enamel because I always paint with acrylics and usually, always need to putty or mask. It also helps you see imperfections in assembly.

I pretty much prime everything. I've found that it gives a really good finish overall, so I prime all but the smallest parts (and even those sometimes).

I only prime spots where I am going to apply putty. I prime before and after puttying. I also prime for Alclad and MM Metalizers, and car bodies to get a super smooth finish.

Thanks y'all! BTW scott...

QUOTE: I do use the Tamiya Fine Surface Primer and have been quite happy with it except on metal parts.

why unhappy with it on metal parts?

Since most of my building is done in resin I always prime. I prefer Alclad or Mr. Surfacer shot from an airbrush. No problems with either over resin, styrene, brass, aluminum, white metal, bass or balsa sealed with CA.

QUOTE: why unhappy with it on metal parts?

Because it doesn't always want to adhere. I painted the nose gear for my A-10, for example, and after a couple of days to let it cure I could wipe it right off. Same for the nose gear on my F-15. On the other hand sometimes it works just fine.

if i use it on some copper wire do you think it would work? whats the best primer i could us e for metal surfaces? can metal primers basically be used for plastics too? thanks

QUOTE: if i use it on some copper wire do you think it would work?

It should. The can states that it is for metal and plastic so I'd recommend just trying it and see if it works.

That's why I was (and still am) confused about it not working on the landing gear I painted with it. It should have adhered fine, but it didn't. The first time I sprayed the parts I let them dry about 12 hours and could wipe the paint off with my hand. I thought perhaps I had gotten it too thick or noat allowed it to cure long enough although I frequently keep going abter about an hour for it to cure. I sprayed it again and used thin coats with plenty of drying time and it did the same thing. I finally gave up and used some Krylon primer and it worked OK, so I don't know what the problem was.

QUOTE: whats the best primer i could us e for metal surfaces? can metal primers basically be used for plastics too? thanks

Automotive primers, in my opinion. They are designed specifically to adhere to metal whereas model primers are designed specifically for plastic parts.

In most cases primers for metal can be used on plastic, but when in doubt try it on some scrap. Many primers are laquer-based and are very "Hot". They can etch the surface of styrene, but seldom do a lot of damage because the thinner evaporates very quickly. Any time I try something I've never used before, I try it on some scrap to see what it is going to do. This is especially true for automotive primers, and the only way to be certain you are using something safe.

Thanks scott.. the tamiya primers are a bit expensive too! thought i'd try an alternative.