So my wife and I are about three months into carving and we’ve started to pick up steady business doing custom signs for professional clients. Our typical go-to for getting, say, a 15" x 20" board to carve a sign into would be to go to Home Depot and buy something like this, this are labeled as “spruce” or “whitewood”. We typically only carve our signs 1/8" deep, or sometimes we’ll go to approximately 1/6" if we’re worried about details not coming through like we need to.
More often than not, after a carve is completed, the outer boards will curl upwards. If you laid the sign on a flat surface, the left and right sides (assuming the long ends of the boards are going up and down) would be 1/2" or less off of the surface while the middle would be obviously be touching the table. I thought that the problem may be with the lamination, so I’ve taken my own 4" x whatever length needed boards and glued them together. I’ve experienced similar problems with the wood bowing after the carve.
Does anybody have any ideas why this would happen? In both instances, the boards are simply butted against each other and glued that way. I’ve made sure that when the boards were glued up in the first place that I had another board on top to press down and make sure the boards stayed flat and level to each other. A few years back, when I was carving signs by hand with a plunge router, I would do this same process, however I would cut some biscuit joints into the wood to give better holding power. This signs didn’t bow then, and it was the same type of wood. Maybe that’s the issue - a lack of internal support along the glue lines? Have you guys experienced similar problems with 1x4 materials?
Moisture is the biggest cause of this and the big box stores have very wet wood. I just did a video showing that very thing. The wood cupped badly. The cause is uneven drying. One side dries faster than the other side. I even tried to dry the wood before carve with no success. I did not realize just how wet it was. Here is the link if you are interested https://youtu.be/4n27WF9gcB4
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Typical indoor hardwood lumber is dried to 6-8% moisture content. Home center SPF isn’t that low when you buy it. You perhaps should check out a lumber dealer and get a moisture meter. I always buy my pine in advance of when I actually want to use it and let it dry out more. Most flatsawn pine warps during that time.
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Thanks Phillip! Great video as always! I may have missed where you mentioned it, but the blue film you use… is that for helping eliminate tear out? Also, does using the sanding sealer help with tear out? We usually use sanding sealer before painting but I haven’t thought to use it before carving.
I’ve got a moisture meter, but I’ve never thought to use it on HD woods like the Spruce that they sell. It feels pretty dry, which I know in truth really isn’t a true indication of a piece of wood being dry or not.
@DanielMiller. The blue film is Oramask 813. The sanding sealer does help with tear out. The wood that the big box stores sell is the worse quality allowed and is very wet
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Phillip has likely identified your issue. Moisture should be the first thing you consider. In addition,
- it’s always good to make sure your applying the same finish or paint to Both Sides of the board.
- Also, depending on if the back of the wood is seen as well as the thickness, you could cut relief cuts in the back, about the same depth as the front. Both of these steps will even up the tension of the wood fibers as the moisture content of all wood fluctuates with humidity and temperature.
- Lastly to repair those signs that are already warped, mount a stiffer backer board like plywood (generally more stable than solid wood) is an option. For this to be most effective, wet the solid wood with a sponge (Wipe off excess) when the surface is mostly dry (But before entirely), glue and screw with short screws from the back of the plywood to the solid wood.
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Thanks for the suggestions Don! What would you think is the minimum thickness of plywood that could be used? Our signs are 3/4" thick and I wouldn’t really want to get an overall thickness above 1" nominal if I could help it.
In my opinion, if it were me, I would use 1/2 inch Baltic birch, and if that makes the overall sign too thick I would experiment with using thinner stock (like 1/2") for the carved sign. That would yield a nice stiff, flat <1" thick sign. Glue the plywood backing on before the carve. No screws. Regular wood glue rolled on thin to both surfaces is how I laminate wood to plywood backing. And I lay it flat with some weight on it to keep it flat while it is drying. Dry it overnight if you can. Happy Carving !
And a footnote, you may have better luck with Poplar that pine both for carve quality and wood stability, plus it is available in 1/2 inch stock at the big box stores. It will cost more but save you time and headaches !
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