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kasunart
12-03-2004, 02:33 PM
I couldn't find much searching this one out, but my question is about the warping of mdf hardboard (masonite type board) and whether you can "unwarp it".
I got 3 of the thickest stuff they sold at Home Depot, on 4 x 8 big sheets, and set them against the wall in my garage. Of course, now they are slightly warped, and it looks like even if I cut them down to small pieces they would still have the curve to them.
Also, on some different but thicker board I'd bought and used before, even though I gessoed all sides really well, it is still slightly curved (and may have been before it was even gessoed.
Any tips on how to treat these situations welcomed! Thanks!
(I'm new to painting on board, its always been canvas.)

Enchanted
12-03-2004, 08:08 PM
I couldn't find much searching this one out, but my question is about the warping of mdf hardboard (masonite type board) and whether you can "unwarp it".
I'm speaking from similar experiences with MDF versus the old "masonite" type of board. I never had any problems like this with the "masonite" types. I've had boards leaning and bowing and they straighten right up when laid flat on the garage floor. NOT SO with the newer MDF boards, I've found. I suppose it has something to do with that MDF designation - medium density - as opposed to the "masonite" which must be high density?! :confused:

And I have no advice for 'un-warping' the MDF. I think if it doesn't "lay down" in a day or two after having been laid flat on the ground, it may need some further coaxing - perhaps a moister environment and heavy weights.

Cochisa
12-03-2004, 10:44 PM
May I ask what kind of saw you use to cut your masonite.?

..I ended up scoring my masonite drawing board when I needed to alter the size to fit my easel. I cut 3 5/8" off the bottom. The first saw was a jig saw...shredded.Then the hack, it shredded the edge too. Next the regular hand saw, same.
I had made a test in a spot that wouldn't matter first. I cut the upper right (rounded) corner diagonally, creating an angle edge to use while I'm trying to sketch them in correctly.
Finally, I used a razor knife and scored deeply across my marked line. It was easy to tap open, then finish with the hand saw and sand a little.
..it has a bit of character now... :D

Cochisa

colin
12-03-2004, 11:25 PM
Hi K,
when you say " thickest stuff " how thick is that ? Like 5/8ths or even thicker ?

You could try bowing it in the opposite direction with a strip of wood in the middle and weights on the ends like Jaxas says ... maybe spritz it a bit with water too. But itll maybe just warp in that direction instead :(

Far as unbowing already painted supports you may have to cradle them unless the frame they are going in is so rigid that it will pull it flat . And then, too the thicker MDF is problematic to cradle -- any ribs you make are gonna have to be pretty thick ! It ends up being really heavy ...

I forget too, to keep em pulled up exactly flat to the wall -- even a little bit of tilt will warp them ...

Enchanted
12-04-2004, 09:25 AM
May I ask what kind of saw you use to cut your masonite.?

My choice is a circular saw with a blade made for cutting hardboard. I use my table saw if the size is small enough to allow it, but for cutting full sheets of hardboard a hand-held circular saw is best. I lay the sheet of hardboard on top of a couple of closesly spaced two-by-fours, flat on the floor. The two-by-fours elevate the sheet of hardboard just enough to prevent the blade of the saw from contacting the floor. You position the two-by-fours parallel to and on each side of your cut line.

kasunart
12-05-2004, 03:10 AM
Thanks for the replies! Thats a good tip about using the 2x4s on the floor to cut with a circular saw. I've been using my table saw, pushing it freehand over the blade unguided (yep, the first cuts are always way off and its a real pain) but once its down to 2'x4' I can get it on my line.
Well, I don't know what to do about these warped boards, what a pain! I'm not sure I want to even try spritzing and weighing them down to fix them.
I think I will shop around for better boards. The mdf's at the home depot are all pretty much warped right off the shelf. Does anyone know what exactly I should try to find, since masonite isn't being made by brand anymore?

Enchanted
12-05-2004, 12:10 PM
The mdf's at the home depot are all pretty much warped right off the shelf. Does anyone know what exactly I should try to find, since masonite isn't being made by brand anymore?
Since you have a Home Depot, look for their bins of "half sheets" of hardboard. If you're going to cut it down anyway, might as well make it easy on yourself and start with the half sizes. I just bought four pieces this past week of the 1/4 inch MDF and there is no warpage at all off the shelf in those sizes. They also sell 2 X 2 ft sheets. As for the masonite substitutes, you can still find similar products, in my experience, but it definitely appears that the MDF is taking over the field. I know that "peg board" is still made like the old masonite and I saw it in the same bins with the half-size MDF. It's usually easy to distinguish between the masonite-type stuff and MDF since the masonite is a darker color.

kasunart
12-06-2004, 10:11 AM
Thanks for the tips Jaxart! Checked out your homepages and love your use of color!

woodciro
01-06-2005, 09:20 PM
My choice is a circular saw with a blade made for cutting hardboard. I...your cut line.

Is this the same as a plywood blade? 60 to 80 teeth?

Thanks, John

Enchanted
01-07-2005, 12:42 PM
Is this the same as a plywood blade? 60 to 80 teeth?

Thanks, John
I think so. It should say on the blade packaging what it's useful for. I often am too lazy to change out the blade to make a single cut and have used a regular rip blade for cutting 1/4 inch thick MDF board with very little chipping along the cut line. I think the key is to have a blade with good sharp teeth, regardless of which one you use.

zacrifice
01-08-2005, 12:07 AM
Lay the boards down with the bow in the MDF pointing up (lay all the peices ontop of each other) then use a little weight to flatten it out and leave it for a few weeks.

It will flatten out and be fine

idylbrush
01-09-2005, 03:34 PM
Once you get it flattened out you may want to consider cradling the final pieces if they are over about 12X12" in size. Cradling will stabilize the panels and make warping a minor issue. Doesn't have to be fancy but it will help.

chubbers
01-24-2005, 04:03 PM
I think I will shop around for better boards. The mdf's at the home depot are all pretty much warped right off the shelf. Does anyone know what exactly I should try to find, since masonite isn't being made by brand anymore

As for the masonite substitutes, you can still find similar products, in my experience, but it definitely appears that the MDF is taking over the field

I did some checking on hardboard and MDF for my own information and posted some comments. Check the two recent replies in this thread on the oil painting forum..... :)
thread link (http://www.wetcanvas.com/forums/showthread.php?t=47595)

Especially, MDF and hardboard are very different products if you are concerned with archival quality of your materials. :)

kasunart
03-08-2005, 12:17 AM
Hey! A little late but I found a use for the large 4x8 foot hardboard (that never seemed to unwarp for the last few months)! I cut it into 32, 12 inch squares. :)
Here's the first few in a long series of squares. Oil/Hardboard 12" square "Maritime" Series

Bevahlee
03-19-2005, 07:22 PM
oh those are really nice, Kasunart.
Here's the deal with masonite. You need to use untempered masonite because it doesn't have an oil base which will after time cause your paint to peel. If it's warped and you have a hot sunny patio, hose it down on the back side. drain it, put some weights at the corners. It should flatten right out. But when I gesso it I always gesso both sides so there is equal tension.

Re: framing for shows...mainly every juror I've ever heard complain about it is..."do not call my attention to the frame. I shouldn't notice it."