prepping wood to make a mold?

[Wes R]

I make my prop guns out of wood and then i'm going to cast them. What should i do to prep the wood before putting it into the RTV to make the molds?

 

[TK648]

make sure all the wood is cleaned up, no saw or sanding dust.
then seal the wood with a clear coat, brush it on first as the wood
will soak up the clear coat, let it dry add a second coat,

then use a clear spray to make the surface smooth......
I think that should do it.....

Make sure you seal off all of the exposed wood
because if there is any un sealed areas in the wood
the silicone will get in and not release, with out tearing

 

[Wes R]

I should have known just to ask you lol. I got a fancy new table top sander that is going to make my life so much easier now. luckily we have a ton of sealants here due to all the projects we've done.

 

[TK648]

I should have known just to ask you lol. I got a fancy new table top sander that is going to make my life so much easier now. luckily we have a ton of sealants here due to all the projects we've done.

After you get your item sealed, let the clear coat dry for a day or two
and before you start making the mold, I would suggest a final coating
or two of paste wax, light coats rubbed on let it haze over then buff it off...

 

[Wes R]

I'll have to get mom to buy the paste wax at lowe's (may as well get a discount). I'm assuming its like furniture wax?

 

[TK648]

I'll have to get mom to buy the paste wax at lowe's (may as well get a discount). I'm assuming its like furniture wax?

yes ... she should find it in or near where the paint is

It's just plain old Johnson & Johnson paste wax

 

[clonesix]

1)Primer
2)primer
3)more primer

sand between coats. sand final coat to 400 grit

Wax, and polish

 

[OzDean]

Just don't seal it because it won't tell you if the wood has enough coverage. Do what the guy above said - primer, primer and more primer...

 

[exoray]

Just don't seal it because it won't tell you if the wood has enough coverage. Do what the guy above said - primer, primer and more primer...

Huh, don't seal it? Sealing wood should always be your first step when finishing it, it's equivalent to primer... Sealing locks down the grain from swelling and helps fill voids in open grain... Sealing is the difference between a zebra print looking paint job where the grain features are flashing through the paint and a hard candy smooth finish...

Personally, I'm a big fan of traditional shellac, apply, sand, apply, sand until smooth sand and then top coat... Shellac has about a 15-30 minute dry time so you can do multiple coats easily in a few hours and because it's a solvent based coating it will self repair and physically bond with the previous layers... You can wax it with paste (car) wax before molding if you want but it's not necessary and might cause issues if you need to refinish the master later... A good top coat of gloss or satin paint will work just fine with silicone, even flat will work but sometimes it has a tendency to leave behind stains and residue in the silicone...

If it's just a quick and dirty mold that you just need the basic shape you can also just lather it in Vaseline and hit it with a hair dryer to soak it in, a quick buff off with some rags and it will mold just fine, but the surface will be rough, I mostly do this with mold boxes and and blocking where it doesn't matter what the surface looks like...

 

[Wes R]

I need to get off my butt and work on this thing. My friend wants it done by Feb and i still have to figure out a ton of stuff x.x

 

[irishamericanlad]

i was posting this in the other thread but 2 times works lol, i hand sanded this down and smoothed out the areas i wanted, then i shellaced it and when it dried i buffed it out with a soft tshirt, then let is sit, i mounted it on a tile and used clear coat to finish it, i buffed it again and cast it. this has always worked for me!
theres a little transfer to the rubber but that comes oout on the test cast...

 

[OzDean]

I meant "just dont seal it - and that's it". I personally use shellac over polyurathanes because the dark colour of the shellac allows me to see if the wood texture has been covered. Only using a clearcoat won't give you enough visual feedback. So I shellac it, sand, sand, sand, then primer, sand, primer, sand, etc...

 

[exoray]

Only using a clearcoat won't give you enough visual feedback.

That could be argued, a good clear coat actually provides a lot of feedback, as can be seen on high gloss wood furniture that shows every blemish and spec of dust... Certain colors do add to to visualization but they can also deaden blemishes as well... Also I find the dull milky color when sanding a clear coat to be very telling of the surface...

You really need to figure out what end finish you want and that will help determine the top coat before molding... A perfect high gloss finish isn't always necessary or desired... A high gloss finish will get the mirror like surface while satin or flat will get a more dulled down one, and you can add texture to the finish by dusting the paint or varying the distance while not wet coating it... A dulled down or textured surface will hide a lot of surface sins...