Steam Bending

[Phil Mueller]

I need to make a curved molding for the base of the apron on a half round table. I’ve never attempted to steam bend anything, but I must say, with the right prep, it worked very well.

I built a steam box out of PVC pipe and purchased the steam kit from Rockler. I do plan to do more, so it was worth the investment to me..around $100 all in. Took about an hour to put the steam box together.

It was probably overkill, but I saw somewhere that it was recommended to pre-treat kiln dried wood. My molding is kiln dried quarter sawn cherry...just shy of 1/2”. I soaked it in water/fabric softener over night before steaming it. Steamed for about 30 minutes, it wrapped around my aluminum pattern quite easily.

I guess I’m just posting to say I’m really thrilled this worked so well. I actually made 4 moldings thinking I would break a few...but it worked great on the first try. Anyone thinking about trying this, well, give it a go. It isn’t as intimidating as it might seem.

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[John C Bush]

I steam bent thin strips for anding nets but never used fabric softener. What's the science/magic for using it. Thanks.

[John Powers]

I needed to bend a load of ribs for a skin on frame (SOF) canoe. Wallpaper steamer from Craigslist worked fine...cheaply. I’ll try the softener next time. It’s strangely satisfying.

[richard poitras]

What is the ratio of fabric softener to water? Basically, how much did you use?

[Phil Mueller]

I used 1/2 cup fabric softener to 1 gallon of water. I’ll have to admit, I made three moldings to bend. Each was soaked for a day in the water softener mix, then steamed for 30 minutes (they are just shy of 1/2” thick). The first one was like a noodle and bent amazingly well. The next two broke. I’m working with cherry, which some say is tough to bend. I’m going to make a couple more and see what happens. If no luck, I will likely look into another wood species and see what happens.

I was thrilled with the first bend. Just don’t know what happened with the next two.

John, I did see a vid on using a wallpaper steamer...probably a less expensive option vs the Rockler one, and I’m sure works just as well.

John B...I saw it recommended on a Wood Whisperer vid and figured it can’t hurt. Apparently it’s recommended if you use kiln dried wood vs. air dried. Air dried is supposedly easier to bend with just steam. Not sure if it has any science to back it up.

[richard poitras]

Thanks Phil for the info.....

[Phil Mueller]

Just to add to my research, apparently kiln drying removes most/all moisture from the wood cells. The cells then set dry which minimizes their ability to re-absorb moisture. Some info suggests soaking in fabric softener for up to a week, but still no guarantees the wood will play nice.

[Mark Rainey]

good stuff Phil! I work with mostly cherry and am interested in your progress on the project. Thanks for sharing.

[Jim Becker]

One important thing here...some wood species are more amicable to steam bending than other species. How the wood is cut/riven also can make a difference. Drying isn't just about moisture, either...the Lignins in the wood change when something like kiln drying occurs and that can materially affect how something will bend, despite the heat and steam being used.

[Phil Mueller]

Thanks Jim, yes, it seems kiln drying changes the wood structure to make it less receptive to bending. And, I understand cherry is one of the more difficult woods. I’m going to try a longer soak. I have also found it to break at the apex of the curve. Going to try clamping there first then working the bend to both sides.

I did purchase quarter sawn with very little run out. Tried to cut the pieces as straight grained as possible.

[Mike Ontko]

Congrats Phil, on picking up a new technique! I'm wondering, did you need to use a backing strap at all to keep your wood from splitting/tearing out? I had a problem recently bending kiln dried cedar, which I thought would be easy, without that kind of support and wondered if the pre-soak would be the way to go.

I use the Earlex Steam Generator and a wooden steam box built with cedar and ACX (pictured below).

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[Phil Mueller]

Thanks Mike, I’m enjoying the process and trying to be determined to get a good piece. I have not been using a backing strap...just applying a zillion clamps as I go around. I do think a backing strap could help. Challenge is that the piece is already profiled and the main clamp point is a small bullnose. So the backing strap will need a reverse profile to hold well. I think my next attempt will be a caul made from mdf with a groove to fit the bullnose. I have a piece of mdf in the right shape, just need to figure out how to carve in the groove.

My piece of cherry will let me get about 3 more pieces made. I’ll give them a good soak and in the meantime work on the caul.

I’m already thinking about plan B, which might be to use poplar and dye it to a kind-of cherry look.

stay tuned...

[Tom Bender]

Phil
Check the temperature in the steam box. Just because there is steam coming out the far end does not mean you start your timer. Put a thermometer into the low point and wait till it goes over 200 F.

It's not necessary to have the strap contact the whole surface (though it helps). Failure is the result of excessive tension in the outer fibers. The strap should put the piece in compression.

[Tom Bender]

Phil
Check the temperature in the steam box. Just because there is steam coming out the far end does not mean you start your timer. Put a thermometer into the low point and wait till it goes over 200 F.

It's not necessary to have the strap contact the whole surface (though it helps). Failure is the result of excessive tension in the outer fibers. The strap should put the piece in compression.

[Phil Mueller]

Thanks Tom. I use a meat thermometer and start the timer when it hits 200. Usually gets up to 210 or so. I’m working on segmented cauls for the next trial. The break is consistently happening at the apex of the curve, so plan is to clamp/caul that first and work to both ends. Have several more pieces soaking now. Will see.

[Bradley Gray]

I bend 1 x 1" cherry for music stand legs. When I started I had a lot of breakage. I've reduced breaks to about 10% by:

Using air-dried cherry.

Insulating my wooden steam box and steaming for an hour at 210.

Using a sheet metal strap and shaping after bending. This made the most difference.

[Phil Mueller]

Thank you Bradley. I do believe the air dried and metal strap would solve a lot of my challenge. I’m hoping the cauls will work as well as the strap...don’t know yet. Do you have a source for air dried cherry?

[Bradley Gray]

I get the cherry locally from a small mill operator - there's probably someone a lot closer to you.

Cauls aren't going to do the same thing as a strap. You really need to keep the wood fibers on the outside of the bend in compression during the bending. I bought a roll of 1" wide sheet metal made to hold insulation in place and drilled holes to attach wood end blocks, one of which was tapped for a thumb screw to tighten against the end of the stock. A game changer.

[Phil Mueller]

Ok, just to follow up. Bottom line; success. In the place of a bending strap, I made a number of cauls from mdf with the bullnose profile. I had the curved mdf from a previous step in building the table, just needed to make the bullnose profile with a carving gouge.

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I doubled the fabric softener solution to one cup per gallon. Then soaked the piece in the water/fabric softener solution for 1 week. It was then steamed for 1 hour. I could tell as soon as I took it out of the steam chamber that the piece was much more pliable than the two previous ones that broke. Using the cauls starting from the center and working out to the ends it bent without an issue.

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No creaks or cracks. I’ll leave it overnight, tie a string to both ends to keep its shape and unclamp. I suspect it will end up being a very usable piece. I have one more piece of molding to try just for fun.

I have no idea if fewer days soaking vs 7 would have worked. I just know 7 days did, and 1 day did not. I also don’t know if the extra soaking was enough or it the cauls were a great assist. I think the cauls helped, but didn’t try it without them, so who knows.

[Mark Rainey]

Glad to hear you solved your dilemma Phil. Keep us posted on your progress. I might try to source air dried cherry for future work. Seems like it would be wise to have some on hand.

[Tom Bender]

Cauls aren't going to do the same thing as a strap. You really need to keep the wood fibers on the outside of the bend in compression during the bending. I bought a roll of 1" wide sheet metal made to hold insulation in place and drilled holes to attach wood end blocks, one of which was tapped for a thumb screw to tighten against the end of the stock. A game changer.

Bradley
The screw to tighten is genius. I'll do that in future.

[Bradley Gray]

Thanks Tom. I have a box of 5/16-18 thumb screws that work great in wood. I chuck the tap in a cordless drill. Not near as fussy as tapping in metal.