alan L | 24 Nov 2017 4:59 p.m. PST |
I have a sheet of 3mm mdf to use as a base for a group of huts as a kraal in Africa. It will measure about 12" x 9". The surface of the mdf will be textured with stones and gravel in between the huts. Do I need to do anything to the mdf to prevent any warping as the glue dries out: I believe I read somewhere that it would be a good idea to paint the other side of the board as an opposite and equal reaction? Any tips would be much appreciated. |
Wackmole9 | 24 Nov 2017 5:17 p.m. PST |
Hi Try and mix the Glue/Paint and Gravel first and apply as a paste. Then place a plastic freezer bag of sand on top. It will evenly press down on the MDF. It shouldn't mess up the surface detail and should stop any warping.
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Baranovich | 24 Nov 2017 5:19 p.m. PST |
Painting in on the back side can work, but I've seen it be hit or miss. Done that and the MDF still warped. What I've gotten in the habit of doing is to apply your texturing to the whole piece of MDF, and then take some really heavy books and carefully place them over each corner of the MDF. You can put a piece of tissue or newspaper between the gravel and the book if you want to prevent any glue getting on the books. That way while it's drying the weight of the books forces the MDF to dry flat. I've done this with cork board bases as well. |
Giles the Zog | 24 Nov 2017 5:24 p.m. PST |
Whilst I have not needed to do this with MDF, I do as a rule paint the underside of any card (black) as you say to provide an equal and opposite warpage. The assumes of course you also paint the "upside" with paint before gluing anything on to it. An example of card warpage and painting is here: link |
14Bore | 24 Nov 2017 5:54 p.m. PST |
The whole point why it warps is you are wetting one side ( with paint) and that side swells and expands. Try a very fast drying primer. Also the smaller the board the less warp it will be. Coating the back side is a attempt to even them out. |
ColCampbell | 24 Nov 2017 6:45 p.m. PST |
Instead of using tissue or newspaper which will stick to your surface, use waxed paper. That is what I used to use at the archives when I was doing book or paper repair. Jim |
TheGaffer | 24 Nov 2017 6:54 p.m. PST |
Here's the technique we use. After two years, no warping at all. Might make rounded bases, and break it up into several smaller pieces. Straight edges will warp more easily. link
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nevinsrip | 24 Nov 2017 8:06 p.m. PST |
Try scoring both sides of the MDF with a sharp blade. I use a criss cross pattern and I do it pretty heavy duty. I have found that it works. Perhaps it allows the board to expand with out warp. |
alan L | 25 Nov 2017 4:12 a.m. PST |
Many thanks for all the tips. Out of curiosity, has anyone tried thn plywood, rather than mdf? Alan |
BTCTerrainman | 25 Nov 2017 8:06 a.m. PST |
I have also found it helps to paint the surface first with a good spray primer before any texturing. This can prevent any water based products from penetrating too deeply into the wood. In the end, shapes do matter as does the materials that you texture and finish with. Water based glues can continue to dry out in dry winter household conditions and can still warp some later. |
14Bore | 26 Nov 2017 5:06 a.m. PST |
Spray primers do tend to dry fast, that is my suggestion, Alkaloid brush on might also as its not water based. |