How to make a steambox for bending wood

A steam box is a handy way to heat wood so that it becomes more pliable than it is at room temperature. Once pliable, you can bend the wood into shapes that you couldn't bend it into cold. Size of the steam box depends on the length and diameter of the wood that you intend to bend. In general, it's good to make the steam box just a little larger than the wood that you're trying to heat. The smaller the steam box, the faster it heats up and the sooner you're bending wood.
I use a short steam box for bending ribs for kayaks. The ribs are 1/4 inch thick and 3/4 inches wide and usually less than two foot long. I use a long steam box for steaming coamings that go around the cockpit of the kayak. The wood for the coamings is about 7 feet long and 3/4 inches by 1-1/2 inches in cross section.

Step 1 Materials list

You will need 5/8 inch or 3/4 inch plywood in the appropriate length. Thinner plywood would work but loses heat too quickly unless you add insulation to the outside of the steam box.
You will need a coat hanger or a few feet of heavy wire as supports inside the steam box to keep the wood off the bottom so heat can get to it from all sides.
You will need a cooking pot. A two quart size is good for starters. You can fill it two thirds full and generate steam for several hours.
You will need a heat source. If you plan on working outdoors, a camping stove works fine. If you work indoors, you can use a hotplate. The hotplate I use runs 750 watts. That is hot enough for the three foot steambox I use and just hot enough for the 8 foot steam box.
Since first writing this Instructable, I have gotten my hands on a wallpaper steamer.  It works much better than boiling water on a hotplate, mostly because it runs at a higher wattage and puts out more heat.  If you can get a used one, go for it. 

Comments

[frisbeechamp1983]

Is it possible to steam wood with glued strips? I have a clipboard that I glued wrong and it's warped.

[nathandance1996]

I would add a indicator bulb and a timer switch to stop that from being left to boil dry.

[cconsultpa]

iam trying to build drum replacement shells out of maple any tips on bending the 1/4" maple around or inside a jig and would it be better to build 3 / 5"high rings and join them or to try and build 1 / 14" ring. Im a complete newbee to wood work especially bending. Any advice would be helpful.

[nativewater]

Not sure about your dimensions and I also have not tried bending maple, but it should work. The best way to proceed is to do some experimentation before buying a lot of wood. There are a number of keys to success, but regardless of your process, having wood with good grain is essential. Grain of your wood should be straight, that is the grain of the wood should run parallel to the edges. Anywhere that the grain runs out of the wood is a place where it is likely to break in bending. The rest of the success story is just a matter of soaking the wood for a few days and finding the right length of time to steam the wood. Try bending the soaked wood before you put it into the steamer. That will give you a baseline of how flexible it is when cold. Then put it in the steamer for about 5 minutes and try bending it again. If it has been heated through, you should notice an increase in bendability. I typically bend around the outside of a form and have some clamps handy to hold the piece to the form. Also search the internet. There are plenty of videos out there of steam bending. Between all of them, you should get lots of helpful hints.

[ilovetea]

I was thinking of making a chair using this technique, one similar to this but with a smaller wood sheet:
http://www.designboom.com/history/choi/22.jpg

[a rigger]

Those chairs, and many like them are made just like regular plywood only with a bent press instead of a flat one. Some heat is useful, but as thin as those veneers are, you should have no problem making that kind of radius curve. If you can source that material in less than railcar-size loads, let me know.

[woodworkingnut]

 I just found you while searching for information on wood bending, but specifically with use of PVC pipe.  This is listed in several articles but my plumbing sources tell me it shouldn't work, due to shape changes in the PVC as the temperature goes up.  I have already purchased a 10' section with a 12" diameter and walls measuring slightly greater than 1/2". Have I wasted my money? Do you have any experience with use of PVC piping for such purposes?  Thanks. 

[a rigger]

I've got two different suggestions if that 12" pipe didn't work. The first is that I used parts from the duct-work guy. I used some 3"x 12" rectangle duct, and plan to someday build a box around it. A couple of A-dapter parts and I was good to go. That works great for wider pieces. Again, if the pipe isn't working... I've always dreamed of switching out my downspouts with 12" pipe. By my calculations 10 feet of pipe holds as much as a 50 gallon barrel. Food for thought.

[nativewater]

I've used 4 inch ID pvc pipe as a steam box.  Works fine with some reservations.  If you're concerned about shape changes, give the pipe some support so it doesn't sag in the middle. 
Secondly, a 12 inch diameter by ten foot long pipe will take quite a good source of steam to get up to temperature.  You will need something more than a one quart pot of water.  Also, the pvc pipe loses heat, so if you put some insulation around it, you won't need as potent a heat source to get it up to temperature.

[a rigger]

In my duct box, I started out with boiling water for steam/ heat, but found I was getting plenty of moisture [maybe too much], but not nearly enough heat. So I added some parts and set my shop heater up to provide the heat. Now I just squirt a little water on the wood and place it in the hot-box for only a couple of minutes. Brilliant! My material is quite thin so It's easy to warm it up quickly without it getting too wet for the glue to set up properly. And, the heater works so well, I won't bother insulating the box at all.

[nativewater]

Yes, having a good heat source is important. I haven't tried bending wood with dry heat myself but heard of it being done.

[tinker234]

very nice job could i make one with plastic bags for insulatun i heard there very good

[Dyyor]

Hi, will this work to bend a 1 in diameter dowel? It is about 4 feet in length.

[nativewater]

success depends on a number of factors. Grain has to be straight. Wood species have different degrees of bendability. Success also depends on how tight a radius you are trying to bend. Success improves if you incorporate some kind of back band into your bending setup to prevent grain tearout. Finally, the thicker the wood, the longer the heating time. Experimentation is in order. And some expectation of early failures helps minimize disappointment.

[abadfart]

can you use this to build a guitar ??

[luneydude]

yes you can place the wood in the steam box and let it get nice and moist and then use an outlinne shape that you want to make the guitar and shape the wood on the inside of that outline shape and then let the moisture evaporate from the wood and youll be good, the wood will try to bend back in to its original shape thats why you need an outline shape so when the wood trys to bend back the outline shape will stop it from doing that. you also want your outline shape to be a little wider than what you want the guitar shape to be, allow for the thickness of the wood your bending. if your trying to make an electric guitar then no unless your making a hallow body like im going to.. if your making an electric guitar, those are built with many layers of wood that are then glued and stack on top of each other the use a jigsaw to cut out the shapes of the peices and then they are sanded down really well to get out all the bumps from where the jigsaw went out of line some companys also use laser cutters to cut out the peices of wood.

[abadfart]

ya im wanting to do a hollow body like a real old gear tech

[luneydude]

yah then you'll just want to decide how thick you want the guitar and decide how long of a length of wood your gonna need to make the side of the guitar then steam it and bend it to the shape, i would use a guitar case as a model for the thickness and shaping it because then you wont have to build a frame to shape it in and then its built to your case and you wont have to buy a new one. then youll just have to cut the front and back of the guiatr, id plase a board over the case witht ape on the board an then take a hammer and lightly tap th e bored on the edge of the case and you should get where you need to cut it, then cut those pecies out. then get some like 1x2's and cut those to make a frame on the inside and then just put it all together and out your neck in and you should be good

[nativewater]

I assume you're talking about bending the sides of the guitar. If that's done with heat, then the steambox would work. You would probably also want some forms to force the wood into the proper shape.

[pquin3]

Could a steam box be used to straighten a warped guitar neck? I would think that a box could be constructed that would contain only the neck portion that needs to be straightened, and which allows the guitar body and the head where the tuning pegs are to extend out opposite ends of the box. Would there be an easier way? Also, it might be tricky to get it to cool to retain a true and straight shape. A straight jig would be important I'm sure. Anything else? Or is the whole idea just a waste of time, trying to fix something that is already toast?

Thanks, pquin3

[nativewater]

The question I would ask would be, what caused the neck to warp in the first place? If it started out straight, then warped, then is steamed back into position, what will stop it from warping again?

Your scheme for straightening the neck via steam and then locking it into a straight shape might work. And if it does, you would be the world expert and could write an instructable about it.

On the other hand, dried wood does not steam bend as well as wet wood or green wood, I assume guitar necks are made from well seasoned wood. Might be easier just to put a new neck on the guitar.

[luneydude]

no actually it wouldnt be easier to put a new neck on the guitar because each neck is different they make them from different types of wood but thats besides the point....necks come in different sizes, then neck you have could be 3" x 4" where it screws to the body and be a 22 fret neck and you could go buy one and it be 3.5" x 4" where it screws on and also be a 22 fret neck plus taking the neck off a guitar isnt good for the body itself...i would take a piece of pbc pipe that has a big enough diameter for your guitar neck to fit in and is about 5 inches longer than the neck, seal one end of it up pretty good (ducktape a trash bag to the end) then place your guitar neck in it hang something that will provide water vapor in to the pipe (i.e. an electric kettle/ also make sure to tilte the pipe with the sealed end sticking up that way the water vapor goes into it), then ducktape a trash bag to the other end but not all the way around only bout halfway around the pipe, and then place a thick blanket over the whole thing to provide insulation and then when the neck is nice and moist go take it and brace it straight (you could take two peices of 2x4 that are the length of the neck and place one on the top and one on the bottom then take two clamps and clamp then together tighly to hold them tight place one clamp on the right side of the neck at the top and the other clamp on the left side at the bottom to even out the pressure pretty well) and let the neck sit and when the water vapor evaporates from the neck you should be good!!!

[blahha]

Use the truss rod to straighten it

[luneydude]

and yah, if your neck is warped then its a pretty crapy neck cause it should warp but maybe 1/8" if it does warped and not even that much the truss rod in it shoul keep it straight thats what its there for, so that the tension of the strings doesnt bend and warped the neck or eventually cause the neck to snap.....so either theres no truss rod in it or you have a very crapy neck or your neck has a crappy truss rod

[otisbaldwin]

thanks a lot! :) I like your kyak it looks like its going to be nice do you have any suggestions on how to make a ball out of wood?

[Thoe37]

from reading your post I am picturing a chair where the person sits inside of the sphere?and since it has been 2 years I was wondering what you came up with

[nativewater]

There's a wooden sphere on the desk of the lumber yard where I get my lumber for paddles. I imagine it was made on a lathe. If you don't have a lathe, you can carve and file using some semi-circular template to check your progress.

[thedude0078]

Thank you very much...much appreciated! ..maybe ill try the wall paper steamer then if i find one for sale..Cheers

[thedude0078]

Just a question which ay be obvios...se the hole in the steam box for steam to get in it is at the bottom right? Thanks

[nativewater]

yes, there's a hole over the cooking pot.
I have since found that a wallpaper steamer has higher wattage than a small electric heating pad and generates a lot more steam.
If you use one of those, you just drill a hole in the steambox the size of the hose on the steamer and run the steam right in.

[otisbaldwin]

what about a hollow wooden sphere? or if i wanted a half of a sphere for a chair im really bad at explaining stuff but maybe you understand what im asking

[isaac!]

any wooden spheres or half spheres youve seen have most likely been made on a lathe. steambending works on one plane (from | to \) not two planes(3D) it could work, but would be exremely ETREMELY difficult.

[mandapander]

I have an end table that has one leg that has a twist in it.If i steam it can i get the twist out of it?

[mauro12mdp]

Seems to be kind of simple =) ...
Should this work to bend something like a bamboo cane ? have you got any tip for bending bamboo canes ?
It's better to bend the cane when it's still green ?

Thanks a lot for the instructable anyway =)

[nativewater]

I haven't tried bending bamboo cane.  I know that people have bent split bamboo. Yes, in general green stuff bends better than dried. Go ahead and try it.  Investment is small

[mauro12mdp]

ok I'll try 
Thanks for your dedication. Then I'm going to tell you how I did the bamboo bending ( or make an instructable for it)

good luck =)

[CharlieHarley]

how long do you have to bend the steamed wood

[nativewater]

not sure about this question, is the question how long do I have to keep the wood in the bent position until the bend will stay? Assuming that this is the question, here is the answer: When you bend heated wood, the bending is a combination of elastic and plastic bending. Elastic bending when released lets the wood spring back to its original shape. Plastic bending permanently deforms the wood. As a practical matter, bent wood has to be locked into its bent shape permanently to keep the bent shape. In general this is not a problem because the bent piece is generally part of a larger structure. If the wood you bend is a stand-alone piece, then you have to experiment to see how much spring back you get and how much of the bend stays. When you steam bend, you probably have to overbend the piece so that after spring back you still have enough permanent bend in the piece. In general, when I do extreme bends, like bending wood into a circle, I leave the wood clamped to the form overnight. Once wood cools, it is less likely to spring back. Also, once it dries, it is less likely to spring back. When bending ribs for a boat, I clamp them in place right away so that the boat locks them into the correct shape.

[altomic]

I used to use 2 aluminium deck chairs, a mattress plastic bag, and a broken kettle. lo-fi baby though there is a certain cool-ness (I can't spell je ne ces que) with this design that leaves it home made looking but bordering on professional in quality/outcome.

[altomic]

re-visit. I used this method to "fix" the tail of my skateboard back in the mid 80's. it seemed to loosen the glue as well as softening the wood and then once steamed leave it clamped for a week or so.