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View Full Version : Using polyurethane to seal birch wood panels..?


3Bak
03-10-2014, 11:14 PM
Done some searching on here and found lots of varying information.. I'm gonna be live painting at a 3 day music festival and want to build a large 4x8 foot birch wood piece out of 2 panels. Since this will be outside and quite possibly the work in progress will be outside in the elements the entire time I want to make sure I seal the wood properly before putting down the first layers..

My plan as of now is to give the wood a few coats (2 or 3) of polyurethane on both front/back/sides. Then layer up maybe 5 or so coats of gesso on the front (sanding in between with a relatively fine-grit sandpaper) to prepare for the actual painting. Anybody seeing any problems with this plan? I'm used to only painting on canvas and actually want to change to wood panels from here on out.. I'm gonna like the rigidity and smoothness of wood already since I'm a detail fanatic, I can already figure that out ha.. thanks for any help! The show is this 28-30, should be a fun gig!

janinco
03-11-2014, 12:54 AM
Be sure to post some pictures here - it sounds like a lot of fun! I'm not sure about the polyurethane since it takes a while to cure, but many artists use KILZ and then gesso. I thought you weren't supposed to put acrylics over an oil base, but it says on the label you can paint over it with oil-based or latex-based paints.
http://www.walmart.com/ip/KILZ-Original-Oil-Based-Primer-1-gal/21190607

Jan

3Bak
03-11-2014, 01:20 AM
KILZ, I'll definitely look into that! My question is will it stand up to the elements outside for a few days though..? Seems perfect for my future indoor work though, I'm a newb to wood panel work so it's all new to me ha. Another question I have as I'm researching, will I need to cradle the panels even if it's the 3/4 inch birch pkywood or will that be thick enough to reduce warping? If not it may be easier for me to purchase the thinner pieces and cradle anyways. May be a bit more difficult when I build my make-shift easel out of 2x4's but want to make sure this will stand up to the elements and be okay for a buyer at the end of the day if anybody is so inclined. Thanks!

janinco
03-11-2014, 02:10 AM
This is from Golden's information page on their Open Acrylics. It has a section on how to prepare the support:

SUBSTRATES AND POTENTIAL S.I.D. ISSUES
OPEN Acrylics can be used on the same substrates as standard acrylics and will display similar adhesion. However, because they are extremely slow drying, using OPEN Acrylics, Gel, and Medium on substrates that contain high levels of water soluble impurities, such as many hardboard wood panels commonly referred to as Masonite®, leads to concerns of S.I.D. (Support Induced Discoloration). This is especially true if working with thicker translucent layers or ones that have been kept wet for extended periods, where moisture has ample time to penetrate into these substrates and allow impurities to be solubized. Because of this, we strongly recommend using MDO (Medium Density Overlay) or furniture grade Birch plywood if wanting to paint on a wood substrate. In addition, we recommend the following as the optimal system for preparing wood supports for use with OPEN Acrylics, Gel, and Medium:

Apply 2 coats of an alkyd-based primer, such as KILZ®, or a white pigmented shellac primer like B.I.N.® Let fully dry.

Apply one coat of GAC 100. Let dry.

Apply 2 or more coats of GOLDEN Gesso, or 1 coat Gesso followed by 1 or more coats of GOLDEN Sandable Hard Gesso.

This is a tutorial on David Kitler's website that shows how he prepares birch plywood for acrylic painting:
http://www.davidkitler.com/classroom-tips1.htm

As far as bracing, I would think 3/4" would not be a problem for such a short time as long as you seal the back, too. If you get a buyer, they can decide if they want to add extra support.

I would definitely keep a weighted tarp ready to cover the paintings if it rains.

Jan

idylbrush
03-11-2014, 07:05 AM
I agree with Jan's advice from Golden. They are one of the leaders in the industry and have an extensive grasp on what will work best. Be sure to use the GAC 100, that will be the barrier coat. I have been using that for many years and it works great.

jmclea
03-11-2014, 09:36 AM
I would definitely go with Golden's recommendations! Sounds a little like a colonoscopy: the prep is going to be the worst of it!
-Jean

3Bak
03-12-2014, 02:14 AM
Sounds like I've got a plan then, thank you! Last question: I'm assuming when doing all this I should coat and prep just the birch panels before cradling--or would I tighten and cradle everything first then apply these layers to both back and front? Thanks again for the help, this was much more straighforward than I was searching up online

idylbrush
03-12-2014, 06:24 AM
It might depend on how you intend to cradle the panels. If you glue the cradling boards you might want to do wood to wood.

3Bak
03-12-2014, 09:44 PM
Yea that was my worry, I've read using wood glue to bind the piece is longer lasting than nails/screws and so on.. I'd thing after sealing the panels that the bond wouldn't be as tight as it should be. So then if I cradle first I suppose I would only be using these sealing products on the exposed birch sections on the backside..?

idylbrush
03-13-2014, 08:15 AM
Sounds like a plan.