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Hi
I would like to paint some picture frames white and finish off with a clear polyurethane finish. The indoor mirror and picture frames are for indoor use and are made of Pine wood. I want to eliminate any corner joins or dents or knotts in the wood. What are the best filler/undercoat/ final white coat paints to use that will be suitable to apply a mineral polyurethane as the final coat?
Thanks for any advice
Michael
Are you trying to get a hard polished plastic look?
Yes it will turn out looking plastic rather than wood. My main question is the type of undercoat paint do I use so that when I sand it back it will eliminate corner joins and knotts in the wood. It seems the slightest bump shows through if you just apply an undercoat and then top coat of paint. I would like to finish off with a mineral (turps based) clear polyurethane coat to make it a really shiny finish. So the paint needs to be compatable with the urothane.
Kind Regards
Michael
It appears that you don't have access to good paint equipment (spray guns etc) and intend using normal household products from a hardware store (turps based paints)
If this is the case then track down your white paint first and then obtain the primers/sealers for it.
First: rub the timber to the best and smoothest finish you can. If there is any bad dips/holes or crack fill them with a plastic filler ( 2 pack filler such as used in the auto trade, Bunnings etc sell such products -"builders bog" or whatever) fill and sand the defects.
Apply the primer, you will need to put on enough that you can sand it down and give yourself a smooth imperfection free surface. 2-3 coats should be enough if the timber has been filled and smoothed properly.
You can then add the white, how it turns out will depend on your ability to apply it properly (flat and smooth) it is easier to spray such a surface than brush it if you are able.
There is no point in applying clear over the white all it will do is discolour the white as it will have a yellow tint to it. So the answer is to get a white polyurethane for the finish. saves a step and makes for a whiter white.
Any product with a turps base can be applied over another turps based product or any other type of paint (water - lacquer or enamel) the turps is not strong enough to attack them BUT you can not put some others over turps based paints as the turps thinned paint will be attacked by them.
Only thing to watch for is drying time, turps based paints dry slow so leave lots of time between coats. At least 24 hours more if you have time, add time if you put on thick coats or lots of them or the temperature is cool ( under 20 deg)
If its radiata pine dont try to remove all the defects/features/joints, its just too soft for that smooth solid colour finish.
Unless you give them a few coats of epoxy/casting resin, tint it with some white tile grout for a plastic look... probably cheaper to just buy some already done.
Got a picture of the frames or are you buying/making them?
Thanks for that detailed advice. The 'yellow tint' in the polyurethane was a great comment because that happened to me before. I thought I had got some wood stain in my polyurethane tin. It really is a mess and ruins the piece. I haven't heard of 'white polyurethane' I might get some of that for the top coat. I have filled and sanded the frames to 400 gritt but I may go back and spend a little more time filling defects with bog and resand. The advice on turps and water based paints and primers was something I needed to get straight, thanks for that. Okay I have the correct plan to achieve good results. Thankyou
Kind Regards
Michael
Is it possible to paint on 'casting resin' do you sand it back or does it become the final finish? I have never thought of using it in that way.
Kind Regards
Michael
If you want an opaque, high gloss finish where you are not going to see the timber, you would be better off using MDF not pine as a substrate - far less filling and fiddling and a much more stable end result - you are not going to get grain telegraphing through the paint in a few years time.
As picture frames are pretty simple construction, I'd say it would be less work to chuck the pine ones out and make new ones in MDF than fill/sand anything that was not totally clear grade pine; I would not want to spend time filling a stack of knots - especially as pine knots can loosen over time.
If you don't have the equipment for a spray finish, I would recommend using spray enamel; it doesn't have to be the expensive cans, I have had good results using cheapie $3.00 stuff.
Fill holes, sand, spray undercoat, spray a few topcoats, and hit with 600-1200 grit and add another topcote or two. After it's dry, you can use a polishing compound on the finish to remove any dust nibs.
If you want to use casting resin, use WEST System or Botecote epoxy instead of something polyester based; its standard practice to overcote epoxy with some sort of finish.
I should have been a bit more exact. Polyurethane is a loose term used to describe what base the paint is. In general people refer to polyurethane as the best option because if you ask "what is the best/toughest/hardest paint?) the answer is "polyurethane".
But it is not the material you will buy in a hardware store unless the store deals in top grade paints. The top grade polyurethane is a 2 part paint which has its own thinner. This thinner is a lot stronger than turps and when the parts are mixed together you get a finish far superior to that of the 'polyurethanes" available in the hardware store.
Top grade polyurethane is used to paint jumbo jets or high class boats or any other surface which one needs the best finish possible. Once mixed and applied it sets into a rock hard coating which is considerably harder to scratch than any turps thinned varient.
If you go to a paint store which sells marine paint and they have a 2 part polyurethane you will be able to buy white or any other colour including clear. Or automotive acrylic urethane enamel is also neally as tough but hardware single pack poly ( one where you use it out of the tin with maybe some turps) is not anywhere near as servicable.
Using these 2 pack products requires you to take precautions due to safety issues, it would be worth your while to take Master Splinters advice and try a can of white pressure pack enamel. The finish if applied nicely will look the same on a good surface and should be good enough for picture frames.
Resins(must be fresh)can be poured/brushed on a surface and allowed to flow out, the surface must be level as possible and raised on pins/nails... the draw back is the rear edges will have drips that will need to be cleaned up. I've only ever used epoxy for this, fibreglass resin can be a bit thicker in viscosity and pool on inside corners. The "casting resin" from Digger's I havent used yet, others here may know its viscosity?Quote:
https://www.woodworkforums.com/images/icons/icon1.gif Hi Harry
<hr style="color: rgb(225, 218, 193); background-color: rgb(225, 218, 193);" size="1"> <!-- / icon and title --> <!-- message --> Is it possible to paint on 'casting resin' do you sand it back or does it become the final finish? I have never thought of using it in that way.
Kind Regards
Michael
Try to avoid sharp 90° edges as the resin will thin out to a few microns on them due to surface tension, round or angle them over a little. Add the colour gradually till you get a solid colour... too much will hinder the flow out and severely weaken the resin.
Its a little trick I learned making car audio trim pieces:)