Introduction: How to Make a Steambox for Bending Wood

Picture of 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

Picture of 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. 

Step 2: Construct the Steam Box

Picture of Construct the Steam Box

Cut the plywood to the dimensions that you need. The interior of the steam box should be large enough so that when you load it up with wood there will still be an inch of space around the wood so that the steam can get to the wood.
Nail or screw the 4 sides together.
Close off one end of the box. Leave the other end open.
Screw a piece of plywood that is 4 inches wider than the diameter of your cooking pot to the capped off end of the steam box.
Cut a hole in the center of the piece of plywood so steam can get from the cooking pot into the steam box.

Step 3: Add Wires to Support Your Wood

Picture of Add Wires to Support Your Wood

Drill some holes in the side of the box to run your wire supports through. Keep the holes the same diameter as the wire to minimize the amount of steam that escapes or the need to do a lot of caulking. The wires will elevate the wood in the box so the steam can get to all sides of it. Cut wires 4 inches longer than the diameter of the box. Run the wire through the holes and bend over the ends so the wires don't fall out.
Finding the hole at the far side by feel is tricky. Shine a light in the open end of the box and look through the hole that you are aiming the wire for. When the light disappears, you have found the hole.

Step 4: Add Legs to Support the Open End of Your Steambox

Picture of Add Legs to Support the Open End of Your Steambox

Set your pot up on the heater that you will be using. Screw some legs to the sides of the open end of the box so that it is level with the top of the pot. The level steam box is important so that the lid of the steam box makes a good seal with the top of the cooking pot.
If you're not that ambitious, you can just pile stuff under the open end of the steambox to raise it to the right elevation.

Step 5: Steam Away

Picture of Steam Away

When you're all set, fill your pot two thirds full of water, turn on the heater and wait for the water to boil. After the water has come to a boil, the steam box still takes a little while to heat up. Once you get a good flow of steam coming out of the end of the box, you're ready to heat and bend. One quarter inch thick ribs heat up in under 5 minutes. Thicker stock takes longer. Heat has to travel from the surface of the wood to the interior. Rule of thumb is 15 minutes of heating per 1/2 inch of thickness.
Keep in mind that some woods bend better than others. White oak, red oak, ash and poplar all bend well. Straight grain is important as well. If you have rain running out of the face of the board, your wood will most likely break where the grain runs out.

It's really easy to leave on the heat when you're done bending wood. Eventually, the water all evaporates, the pot becomes hot and the plywood starts smoking. Good way to start a fire.


pquin3 (author)2010-09-26

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

kloosterross (author)pquin32017-11-06

I saw a technique for bending the sides of the body of a musical instrument using a wet rag around a large soldering iron. The wood is worked back and forth across the saturated cloth covered iron while applying pressure to bend it around the iron. I haven't actually tried this but it seemed like a good way to only apply the steam to the area of the bend.

nativewater (author)pquin32010-09-27

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 (author)nativewater2011-06-07

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!!!

josuchav (author)luneydude2015-08-13

true dat!

blahha (author)nativewater2010-10-17

Use the truss rod to straighten it

luneydude (author)blahha2011-06-13

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 either theres no truss rod in it or you have a very crapy neck or your neck has a crappy truss rod

Boltazar (author)2015-08-13

I have to replace my oil fired steam furnace this fall. I was thinking of setting up a valve system allowing me to use it to steam wood all year round. Wouldn't be to hard to do. Auto water feed and such. Might b too much steam. Any thoughts?

nativewater (author)Boltazar2015-08-14

Temperature of the steam depends on what sort of pressure your heating system is at. Primitive steam source of the type I've illustrated operates at atmospheric pressure and the steam is somewhere around 212 degrees, hot enough to bend wood but not so hot that you're in danger of getting hurt. As long as you have a way of keeping your heat chamber at atmospheric pressure, you should be alright.

Boltazar (author)nativewater2015-08-14

Thanks for the reply, I'm very new here. Sleeping on this concept last night I thought I might be producing to much steam. Or waisting oil. Any suggestions for a type of hose to run from the back of my house to the shop, about 40'?

kloosterross (author)Boltazar2017-11-06

Distance between steam source and steam box is your enemy. Unless very elaborately insulated you might end up with hot water at the end of the line, or at least a significant amount of condensate.

charlessenf-gm (author)Boltazar2017-01-03

Forty-feet! Really? It would need to be steam-pipe just like the stuff that carries steam to the radiators (for instance). Iron pipe? And, if it needs to span forty feet, think of several inches of insulation unless you want to fill your steam box with hot water.

jcmschwa (author)2017-06-08

Would foil wrapped around the end with rubberbands to keep it tight work better than a towel?

Kevin W2 (author)2017-03-11

Is mahogany good for bending? I am constructing an arched arbor for our wedding and am thinking of using a steam box. My other thought, to have less waste, was to have the wood for the arch mimic puzzle pieces. Any thoughts?

jossy (author)2016-06-21

Hi can I use a pressure cooker as a boiler for the steam?


charlessenf-gm (author)jossy2017-01-03

A Home Pressure Cooker comes with a relief valve designed to allow steam to exit before the pressure builds sufficiently to deform or 'blow' the cooker.

I suspect a copper tube could be fitted to this orifice to carry steam to your steam box.

Not sure of the advantage - save the locking lid allows for piping all the steam generated provided you can create a steam-tight conduit. between cooker and steam box.

wolfgang.brinck (author)jossy2016-06-21

yeah, presuming the pressure cooker has some place to hook a hose up to that lets you transfer the steam to the steam box.

GargoyleBard. (author)2016-05-03

I'd like to make a Crumhorn, and doing so requires bending a length of wood with a hole drilled through it. Have you ever tried something like this, bending a tube with a hole? I feel like it should work, but I'd rather know for certain before trying it...

LouisC55 (author)GargoyleBard.2016-07-27

This is definitely possible, I have made a smoking pipe using this method. The hole can deform in the process of bemding, so I recommend putting a thin piece of wire through it as you start to bend it. Other than that, the method should be much the same, and quicker as the hole increases the surface area of the wood.

GargoyleBard. (author)LouisC552016-07-27

Ah, thanks! I was mostly worried about the hole deforming, so thanks for mentioning that! How would I know how thick of wire I need to keep it from deforming too much?

LouisC55 (author)GargoyleBard.2016-07-27

It depends how sharp an angle you're bending it at. If the bend is at a large angle, the hole will end up smaller no matter if there is wire in it or not, in which case the wire could get stuck. The thinnest point will be roughly half the diameter of the initial hole for every 90 degrees you bend the tube by. I used a wire coat hanger, but any smooth wire will work fine if its a little smaller than the hole. Also, make sure to check the wood you're using copes with steam bending (my favourite is black walnut, it bends brilliantly, has a beautiful grain, and is very strong). Its much easier than it sounds actually, just make sure you don't steam for too little time, or when it dries it can splinter.

GargoyleBard. (author)LouisC552016-07-27

Alright, thanks for the info!

LouisC55 (author)GargoyleBard.2016-07-27

Just to clarify, if the bend was 90 degrees and as sharp as possible, then the minimum diameter would be half the original. If 45, it would be 3/4 of the original, etc. If the bend is less sharp then the size will change less, and you could use a larger wire. Make sure its smooth or it will get stuck!

MrMxylptlyk (author)2015-12-08

hello. nice tutorial. I am wondering if steam bending wood reduced its strength, springyness. I am considering recurving a bows limbs with steam.

cconsultpa (author)2012-04-08

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.

josuchav (author)cconsultpa2015-08-13

Again I see an old question I'd like to chime in on.

Did you ever try it? I would love to see them if you finished them. That's one of those projects on the list that I haven't had a chance to get to.

I wanted to share with you what I thought was the best solution along with a few more DIY ideas I have for it. Luthiers have a bending iron that is used to shape the side of the guitar. This may not be the most cost effective way for a one off diy type of scenario though. At time of posting they range from $80 to a few hundred.

That brings me to how I will do it once I get to the project.

Two options: make a bending iron by starting a fire inside a large metal pipe that is smaller in diameter than the drum (I don't think I'll try this for my first attempt)

Option two and the one I'll go with first: make a form for the internal diameter of the drum. Buy veneer material for the shell. cut a rectangle as wide and long as the height and diameter of the desired shell. put water in a metal pan big enough to fit the wood in and set it ontop of a heatsource to bring the water to a boil. Stick the veneer in and bend it over the form holding it down with straps, rope or rubber bands depending on size.

Repeat for several layers leaving the previous layer on the mold to compensate for size and measuring the diameter again. Each layer will obviously have a larger diameter than the last. also, the grain direction should be alternated to provide structural strength as well as warpage prevention. The edges of the veneer at the seams will need to be planed an angle for them to butt up properly.

once you have enough layers (needs to be an odd number of layers. something to do with how the wood will warp if plywood is made with an even number of layers) glue them one by one with generous ammounts of glue between each layer, one at a time and alternating the location of the seam to avoid a weak spot. moving the seams around the circle will prevent having one solid seam.

Sorry if this is now superfluous. Just wanted to share in the brainstorming.

nativewater (author)cconsultpa2012-04-09

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.

mauro12mdp (author)2010-01-06

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 =)

josuchav (author)mauro12mdp2015-08-13

I know this is old, but wanted to answer the question. Bamboo bends best if you treat is as if it were PVC. Sounds weird, I know, but try it!

I would soak it first just like nativewater said, but get you a plumbing blow torch (or if that's not an option some sort of medium fire that lasts a while. Maybe an oil lamp with a really big wick?) and apply the heat directly to the area that needs bending.

Bamboo is really springy so you'll want to bend it further than your final bend needs to be. I don't have a percentage as I've never needed to be that specific, so you'll have to experiment. Sorry. Also, you'd probably have best results if you have a way to fix the the bend until it dries because of that springiness.

nativewater (author)mauro12mdp2010-01-06

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 (author)nativewater2010-01-07

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 =)

NectarineSoup (author)mauro12mdp2012-09-20

Hey did you try bending the bamboo? I'm looking into bending and setting cane at the moment and have a feeling they might have similar properties...?

mauro12mdp (author)NectarineSoup2012-09-20

Yes I tried but the canes might had been too green for bendings or I don't know. The problem was that the canes got degraded and lost its hardeness. I suppose that due to environment, humidity and funguses. I guess that if you wanna try this, you should keep an eye on the place you store them so as not to have the same problems.

Good Luck with your work =)

Bigolkj (author)2013-10-02

what kind of wood makes good crossbow limbs that I can maybe buy at the home depot? I have been making cross bows out of fresh cut wood, and wanted to step up the quality..message meback if you know any tips.

Boltazar (author)Bigolkj2015-08-13

Ask or hickory or oak. Try to use green or air dried wood. Kiln dried is not as bendable.

cmacarthur (author)Bigolkj2015-03-10

Hickory, if they have it at home depot, is a good choice for pretty much any kind of bow. being a semi professional bowmaker myself, i have used hickory boards from menards many times with very good results, no difference in cast between the boards and the staves. if youre really serious about bowmaking, the key is spirit and perseverance, not access to premium woods like osage orange. really, i wouldnt risk an expensive wood like osage orange on a starting bow anyway. hickory boards are much cheaper, so when they break ( everyone breaks a few, especially starting out) you aren't out very much. Red oak is a popular bow wood for beginners, though it has less than optimal cast and some less than satisfactory shooting qualities, it makes an average to good flat-limbed pyramid style bow, and i have even seen semi-english longbows made from it. the key is not throwing your money down the drain to break your bow and your heart, its putting your heart into what you do. eventually you will come out with a good, dependable bow, and a whole lot of pride in what you made.

myoung49 (author)Bigolkj2014-06-21

If your serious about making a bow whether it be a cross bow or a long bow always do your research. The wood traditionally used for making a bow were hickory and lemon-wood, or bamboo and yew. if these types of wood are not available in your area then you have two options, find substitutes for the above timber or go to an importer that imports the material from whatever country where it is grown. I hope this helps

bluesharp1359 (author)Bigolkj2013-12-10

Your best bet would be to go with Osage Orange. Very popular in the best long bows, recurves, etc. Do an ebay search for Osage Orange bow staves

nativewater (author)Bigolkj2013-10-17

Good luck with Home Depot. Where I'm at, they have pine, poplar and red oak in clear lumber, none of which is typically used for bows. Try to get some hickory or ash if you can at a wood place that targets cabinet makers.

Richo59 (author)2014-12-26

Is all timber able/suitable to be bent by steaming?? I have a architrave that has rotted and needs to be replaced it is 1 1/2" x 3/8" bent to a radius of about 2'. Existing timber is Australian Silky Oak (not real oak though).

zacker (author)2013-07-01

Hey, anyone have any idea why I cant post or reply to anything except for places I already posted to before? Like this instructables? this has been going on for about 3 weeks now. I cant even post to the boards or forums here, only to instructables I posted to prior to a few weeks ago. What's changed?

zacker (author)zacker2013-07-01

oh sorry for posting my problem here but I cant post it anywhere sorry.

ardnon (author)2013-01-16

Very nice, very simple, I want to try it... thinking of making a wooden toboggan...

woodworkingnut (author)2010-04-26

 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. 

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.

Bowmite (author)nativewater2012-07-01

Hey guys, I've never bent wood but am thinking on making some snow shoes. This is the first reading I've read about making a steam box and have thought of using PVC. Kinowing the basics and the characteristics of such, I didn't know if it would work well. My next thought was of using double or triple wall stove pipe. What do you think?

a rigger (author)nativewater2012-05-10

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 (author)a rigger2012-05-16

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

a rigger (author)woodworkingnut2012-03-28

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.

frisbeechamp1983 (author)2012-05-04

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

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Bio: skin on frame kayak builder since 1987
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