Sandpaper and Primer. Should I use them and which one

I prime almost everything, except very small styrene parts. I always prime bare metal.

I use wet or dry sandpaper in fine grades, usually sold for auto painting rather than woodworking.  I normally use either 400 or 600 to sand primer, 1000 or finer to sand color coats.

As far as what you are talking about,I don't think there is a need to sand off the old paint.I think priming alone would be fine.I use Tamiya,or Mr Sufacer 1200 in the rattlecan,but many swear by Krylon.As for sandpaper,many hobby dhops sell packs that include sheets of all diffrent grits.

Also instead of using the General Forum,in the future try to place you question in the appropiate topic for the simple reason you will get more looks.

And welcome to the forums.

I paint stuff like that all the time. Just prime it and go. As far as sandpaper, I personally wouldn't bother.

sherbir

can I use the white wall primer to prime the model?

No. 

Definitely NOT if you are talking about the stuff that comes in a bucket/can that goes on walls!

We are talking a primer here that comes in a spray can.

You can spend anywhere from $10 a can (small) for Tamiya to $1 a can Walmart ColorPlace (or whatever its called now). The difference being the Tamiya is a much finer (smooth) finish. Well worth it if you are doing something you want to have a showroom finish like "a brand new car"!!!

Many people use Duplicolor from auto supply stores. The cheap Walmart brand is also popular. I have mixed feelings about Rustoleum. I've had problems with it. I do like their camouflage colors.

I keep primers in white, light and dark grey, black, and rust (red). The color I use is based on what color the model is going to be. I don't kmow if it makes any difference but it should!!!!

No. But you can use cheap rattle can primer with good results. I get mine at Pep Boys for under $4 a can (2 for 5 on sale).

I use Krylon primer- get it from Walmart at a similar price.  I learned about Krylon primer from the old newsgroup rec.models.scale, and have used it for at least ten years now.

Thanks everyone for the insightful answers. But here's the problem. I live in New Delhi, India. I have been to numerous small and big hardware stores and paintshops looking for a plastic primer without any luck. Whenever I say I need a plastic primer, the shopkeepers either simply shrug it off or say there's nothing like that available. Surprizingly, they all tell me to paint straight off on the plastic, which I don't wana do. So either the plastic primer is called by some other technical name out here, which I do not know, or there must be something missing. Its been a week of searching for it, to no avail.

Hobby shops are very rare here in my country and all you can get here is paper art stuff. Can someone help ? There's not much available on the internet also about plastic primers in Delhi

Ok, that's more insightful. Can you access international hobby store websites? Can you receive paint through customs?

There are several online hobby stores which have exactly what you need. But first you need to know what you need. Take a look at websites such a these.

www.scalemodelguide.com/.../primers

Steve

Flat black spray paint! Wash and dry parts first.

"...either the plastic primer is called by some other technical name out here, which I do not know, or there must be something missing..."

I suspect that asking for "plastic primer" is what's throwing you off. Just ask for a spray primer. I've been painting models of all types for years and I've been using generic spray primer for almost as long. Of course, you can always order up a Tamiya primer online or from eBay. I've used it with good results (only because I found a great deal on a case of it on eBay, in fact), but it tends to be pricey, imo. If you're worried about the primer reacting with whatever material you're spraying, do a test on a scrap or nonvisible area first, but I've only had a bad reaction to cheap primer once and I suspect that was more because of the cruddy, self inflicted paint job I was trying to cover over.

Krylon primer is not unique to plastic models. It is a generic primer.  It works well on styrene plastic or urethane resin.  Many auto body primers also work- I have friends that use those.  Maybe look for those in auto parts store.

sherbir

Thanks everyone for the insightful answers. But here's the problem. I live in New Delhi, India. I have been to numerous small and big hardware stores and paintshops looking for a plastic primer without any luck. Whenever I say I need a plastic primer, the shopkeepers either simply shrug it off or say there's nothing like that available. Surprizingly, they all tell me to paint straight off on the plastic, which I don't wana do. So either the plastic primer is called by some other technical name out here, which I do not know, or there must be something missing. Its been a week of searching for it, to no avail.

Hobby shops are very rare here in my country and all you can get here is paper art stuff. Can someone help ? There's not much available on the internet also about plastic primers in Delhi

You can apply finished coats to plastic, or metal, for that matter, without priming, but priming helps ensure that your paint will adhere the best.

If you can't get anything to use as primer, then you want to make sure that the surface you're going to paint is as clean as it can be, especially free of grease or oils.  You could try using an automotive de-greaser (I use one available here in the States, Super Clean), but you could also use dishwashing liquid, which is likely to be formulated to remove grease.  A couple of drops in some warm water should suffice.

As far as primers go, if you can't find any locally, try the Internet.    I would try Tamiya's website.  I started using their rattle-can surface primer, and found it to be nicely fine-grained.  Here is a link to the item in Tamiya USA's website:

http://www.tamiyausa.com/items/paints-finishes-60/finishing-supplies-62000/surface-primer-plastic-metal-87026

but I'm sure you could probably  order it from Tamiya in Japan, or through sellers a little closer, like Hong Kong or Singapore, if there aren't any local who carry it.

Tamiya also makes a lacquer-based surface primer ("Surface Primer L" in three colors), but I haven't tried it.

I used to use automotive primers (WalMart's store brand), but the last few cans I got all clogged with nearly all the paint still inside the cans.  It's cheaper, but it's not quite as fine-grained as primers made by modeling companies, for modelers to use.

And if you can't get spray primers, there's no reason you can't get a jar of paint and use it as a primer.  There's the Mr Hobby line of products, also made in Japan.  I even used to use Tamiya's acrylic Flat Gray as a primer on my toy soldiers, brushed on by hand.  Again, make sure you have a clean surface, and I would also thin the paint, but thinned down, brushed on by hand, you can get a nice smooth surface, with care.

Hope that all helps!