priming wood for painting help?

[ObiWannabe]

Hello RPF! Long time no see!

I come to the experts with another dumb noob question. I searched the forums for a similar thread but nothing came up, so here we go.

I'm working on a set of katana (for Zoro from One Piece) out of wood. I've already planed the blades and am about to move into the sanding phase, so it's time to start thinking about painting. I would love to be able to fool people into thinking my wooden swords are real metal, so I'd like a really super-smooth finish. I could use some tips on how to get there.

Everything I've looked up on the subject of sealing wood prior to painting so that it doesn't soak up the paint or show wood grain involves strong chemicals and lots of sanding. Repeated sanding of multiple layers of sealant. I want to know if this is, literally, the only way to seal wood in order to get a super-smooth glossy finish, or if there are some hidden tips and tricks that you guys have figured out. I don't want to have to use polyurethane sealers and other strong chemicals because I live in a small apartment and don't have access to a work area, good ventilation, etc. At least, not until the weather warms up. But if that's the only option available, I'll stuck it up and buy some safety masks.

The blades are poplar, while the tsuba are layered basswood filled in with paperclay. Both the blades and the tsuba need to be sealed after sanding so I can paint them. I'm just being anal in not wanting the wood grain or sanding marks to show through the paint, I admit, but I want these props perfect in every way. Thanks for any help you guys can offer!

 

[James Kenobi 1138]

Use sanding sealer. It's the correct choice because it works.

You can brush it on or get a spray, but for maximum smoothness you do need to do 1-2 coats. Then primer, and you might want to go 1-2 primer coats with wet sanding in-between.

 

[exoray]

Use sanding sealer. It's the correct choice because it works.

And may I suggest traditional Shellac, it's been used for 1000s of years for a reason... There are now synthetic grain sealers but there is no real reason in most cases to not use Shellac...

As for multiple coats and sanding between them, yes that is what you will need to do... If you want a mirror finish you will need to work it out, but using shellac that has a 15-30 minute dry time you can do several coats in a very short time and get that mirror finish in a few hours time...

One word Shellac, it has a strong smell, BUT it's only the evaporating alcohol it's dissolved in, it's not some incredibly toxic chemical it's just grain alcohol... It will of course make you loopy if you sniff too much just like any potent booze will, but with basic ventilation you will be fine... Crack a window and use a fan... Once dry it's 100% non toxic and actually FDA approved for human consumption... It's still used by many high end candy manufactures to coat candy so that it's not sticky...

And when using shellac primer isn't necessary as shellac serves that purpose as well, but it never hurts to use a primer coat... I generally do the primer coat after the shellac just for a color difference so that I can wet sand out that primer and make it sparkle...

 

[James Kenobi 1138]

I agree, because most sanding sealers are clear shellac, so you can't go wrong either way.

 

[exoray]

I agree, because most sanding sealers are clear shellac, so you can't go wrong either way.

Yeah most are but I have come across a few that were not, so it's always good to specify... The other formulated sealers I have used did work at sealing the grain IMO they didn't work as well or were they as user friendly as good old shellac...

The synthetic sealers are generally a better choice for exterior wood work as ammonia (animal urine and bird poop) will break down and destroy shellac...

And that is another nice feature of shellac, household ammonia for removal or clean up... But be aware it DESTROYS the shellac so don't use ammonia as a thinner or what not make sure the brushes are ammonia free after cleaning before re-use...

 

[BAK55]

In the past I have hidden wood grain to create the illusion of a metal surface by just using poster board as a veneer. Once the seams were sanded and blended I'd seal the veneer with a mixure of white glue and water then sprayed on a polyurethane coat or two before painting.

 

[robn1]

You can also try Minwax Polycrylic. It's nontoxic and forms a very hard finish. It comes in tins and spray cans.

 

[Darth Detroit]

Sand sealer is the way to go. There is also a water base type made by Minwax thats a little easier to use. Sand between coats, use a nice primer, sand again, primer then paint. sand again...:thumbsup

 

[HadronMM]

The really important missing step here is that you need to do what woodworkers call "raising the grain." After you've sanded the pieces down to 300 or so (a higher grit won't make any difference on wood that will be painted) but before you start sealing, or painting, you need to run a wet sponge over the pieces and get the surface wet. You can use just water for this or alcohol for something that will evaporate quickly.

When you sand, you compress a lot of the wood fibers down into the grain. Raising the grain will make those loose fibers swell up and come out again. Once that dries, you hit the surface lightly with your high grip paper and take all those new sticking up fibers off. That will open up the pores of the wood for your finishing phase and it will get the surface smoother.

I suspect that if you build up some layers of primer with light steel wooling between, and then build up several layers of paint, you can get a really smooth, reflective surface even without all the sanding sealers or fillers. But with that said, a good wood filler pressed down into the grain (after raising the grain) and allowed to dry, will give you an even smoother finish.

MM

 

[exoray]

The really important missing step here is that you need to do what woodworkers call "raising the grain." After you've sanded the pieces down to 300 or so (a higher grit won't make any difference on wood that will be painted) but before you start sealing, or painting, you need to run a wet sponge over the pieces and get the surface wet. You can use just water for this or alcohol for something that will evaporate quickly.

First off as I said earlier there are different kinds of sanding sealers, there are those who's sole purpose is to raise grain for sanding and prep for another top coat and there are those that raise the grain and also fill and lock down the grain...

Shellac is a raise, fill and lock sealer, it soaks in and raises the grain, fills the grain and than locks down the grain all in one step... Shellac also serves as a very universal primer coat for many different types of top coats...

Now if you use a simple (non-shellac) say water based sanding sealer designed to simply raise the grain for final sand out on say a stain or wax finish it's a whole other ball game... But when using shellac no pre-steps or additional grain prep is needed, the first coat of shellac takes care of that entirely...

I suspect that if you build up some layers of primer with light steel wooling between, and then build up several layers of paint, you can get a really smooth, reflective surface even without all the sanding sealers or fillers.

No need for multiple layers of primer after the 2-4 coats of shellac that were sanded lightly between coats you are ready for top coat(s) at that point the shellac is the primer... As I said I sometimes use a tinted primer (generally I just use white tinted shellac) right before the top coat just to give contrast on my final sand before top coating...

But with that said, a good wood filler pressed down into the grain (after raising the grain) and allowed to dry, will give you an even smoother finish.

With 2-4 coats of shellac unless it's huge open grain wood or has holes or imperfections no additional filer is necessary, the sealer will fill any and all grain lines by itself... I have removed all traces of grain in open grained woods like oak with 2-4 coats of shellac...

Honestly once you use shellac and see what it's capable of you will highly appreciate it... It's one of those products that works better than advertised...

 

[ObiWannabe]

Oh man, I knew I could count on you guys.

A couple of coats of sanding sealer (whether water-based or shellac or what) is manageable. I'm pleased to hear about varieties with far less toxic chemicals than the ones I was finding on modeling boards.

Hadron - amusingly enough, that's a step I'm used to after working with paperclay. I usually make my final sanding a 400 grit, and then use water to wet the paperclay dust and seal it back into the sanded clay - it makes for a porcelain finish. I will make note to do the same on the wood.

Of course, sanding all the tiny crevaces in the tsuba might be tough, but we'll see how it goes.