Author Topic: use of sanding sealer and primer (Read 3163 times)

kvarley · « **on:** November 10, 2008, 12:16:29 PM »

What is the deal with sanding sealer and primer . What is their intended use as far a finishing a doped stunter?? Are they basically the same stuff?? Does the use of talc/dope eliminate the need for them. Keith Varley

FLOYD CARTER · « **Reply #1 on:** January 25, 2009, 02:57:42 PM »

I don't understand or agree that sanding sealer or primer has to be sealed with a coat of clear. I typically mix talc in clear Brodak for the first few coats (brushed or sprayed) and immediately go to colored Brodak dope. There isn't any problem with adhesion or bleed-through (except that yellow dopes do not cover well.). I've used Brodak primer followed immediately with the colors. Still OK.

Floyd

Wayne Collier · « **Reply #2 on:** January 29, 2009, 05:43:08 AM »

While it is true that more than one technique will work, the arts of sanding, sealing, and priming are very important to the finished quality and durability of any paint job. There is also a lot to be said for familiarity with the characteristics of which ever kind of paint you are using. With practice and careful experimentation you will also learn which products work well together and which techniques fit your style -- things such as which kind of topcoats stick to which basecoats and what color primer or base coat will give the best look to your finish color. You may even develop a preference for certain brands or styles of masking tape or trim brushes.

About twenty-five years ago a friend of mine got interested in model rockets. He bought several kits and asked me to build one. These were the old cardboard tube / balsa fin type models. At the time he was working as an electrician and I had been finishing cabinets and other wood work in custom homes and offices. After I glued the rocket together I shot on some white tinted primer sealer like I had been using for some things at work. I then carfully sanded the rocket, removed the dust and then hit it with a coat or two of white krylon from a spray can. I then painted the "north" fin with olive just to give the thing some color and put on a few decals that I had left over from some other modeling projects. It really wasn't all that special but compared to the ones he had just glued together and brushed with the finish color, it really stood out. After looking at it for a few minutes he said "How did you do that?" It wasn't just skill -- it was knowing a little about priming, sanding, and topcoats that made the difference.

Wayne Collier · « **Reply #3 on:** January 29, 2009, 06:09:32 AM »

Sanding sealer seals the grain and will often lift loose wood fibers. After the first coat of sanding sealer the wood may have a rough fuzzy feel to it. This lifted loose stuff will then sand off more easily. With out the sanding sealer lifting and stiffening these fibers they will be limber and lay down under the sand paper and may not be removed by the sand paper and will often stand up and fuzz up the paint job at a later point. Also sanding sealer isn't as tough as some later layers of paint so it sands easier and helps yield a smother surface. While the sanding sealer helps get rid of unwanted fuzz, filler helps level up tiny crevices and and other low places. Commercial premixed filler coats are available. While I haven't personally tried it, I understand that a little cornstarch in some clear dope will do the same thing. It may be that the proper mix of corn starch in clear dope will serve as both sanding sealer and filler helping to get to that smooth surface a few steps quicker. After the surface is filled and smooth, primer gets it ready for the color and topcoat. For some colors and topcoats clear dope works great as a primer. As Ty said though, you may find that choosing the right color primer will enhance the look of the finish color. Also some kinds of paint will require specific primers. After the color is applied, many people like to put on a coat or two of clear finish as a protectant and to add some shine. If you used dope for the color, clear dope often works well for the final clear coats also. Some kinds of paint will do better with other kinds of clear coat.

Never be shy to read the side of the paint can.

Brian Massey · « **Reply #4 on:** January 30, 2009, 05:02:30 PM »

OK, here is the picture I lost before:

Brian Massey · « **Reply #5 on:** January 30, 2009, 05:18:31 PM »

Well I can tell you what not to do! I'm just getting back into C/L after a 35 year layoff and am building a new Ringmaster and rebuilding a 35 year old 'master. I was ready to finish but had no dope so I got clever and used polyurathane. Went on nice but then the dope I ordered (Reynolds from Aircraft Spruce) came and I thought; "hey, add some color!". I can tell you for sure that pulling masking tape (3M blue) pulls dope right off of polyurathane.

Keep all hints and suggestions coming, I'm reading them and they will help me regain my lost finishing skills; I nee all your help!

PS: I posted this before with a picture, but I got an error message because the picture was to big, I resized, reposted and then it gave me another error saying I had already posted (couldn't find it) , then I reposted just the picture, and it came up, but no verbage, so here's this. Maybe I'll learn out to use this forum sooner or later. Sorry if I'm causing confusion.

Brian

Brian Massey · « **Reply #6 on:** January 31, 2009, 11:06:56 AM »

Hey Wayne; What ratio of cornstarch to clear dope do you like? In the past I have used dope and talc, but if you're not careful the weight can build up.

Thanks,

Brian

Wayne Collier · « **Reply #7 on:** February 01, 2009, 12:33:40 PM »

I just reworded my previous post about filler coats in hopes of more accurately reflecting my experience. I have never personally used the cornstarch method. The recipe I've seen is one part thinner / one part dope / one part cornstarch. The truth is that so far I've skipped the filler coat on most of my models and just lived with a little wood grain and some other minor imperfections showing through. I have used nitrate dope mixed 50/50 with thinner as a first coat on models, and I think I used a cellulose lacquer based sanding sealer on one recent model that is similar to what I have used on cabinets and other wood work. That model (a 1/2s sheet wing) was later coated with tinted and clear polyurethane. For painted wood work in houses back when I was doing that for a living I used an enamel undercoater that had very heavy solids. Maybe too heavy for model use.

Author Topic: use of sanding sealer and primer (Read 3163 times)

kvarley

use of sanding sealer and primer

FLOYD CARTER

Re: use of sanding sealer and primer

Wayne Collier

Re: use of sanding sealer and primer

Wayne Collier

Re: use of sanding sealer and primer

Brian Massey

Re: use of sanding sealer and primer

Brian Massey

Re: use of sanding sealer and primer

Brian Massey

Re: use of sanding sealer and primer

Wayne Collier

Re: use of sanding sealer and primer