How long to boil green rough-turned vessels

[Rob Miller]

I'm in Arizona and there's a real problem with cracking due to very low relative humidity. I've been boiling some smallish (8"-10") bowls in hopes of reducing cracking during drying. I'm wondering how long I should be boiling? I've been letting them boil at a low roll for about 2 hours or a little longer if possible. Who else is using this technique and what are your experiences with boiling? So far I'm just doing hickory and mesquite (I think it's Chilean mesquite). The mesquite seems pretty stable except for around knots but the hickory is really prone to cracking. REALLY pretty wood, though.

[bob svoboda]

Just had a boiling lesson from a very fine local turner. His method is 1 hour per inch thickness. He also maintains that you can under boil, but not over boil. What you are looking for is a uniform temperature throughout the piece.

[Rob Miller]

Just had a boiling lesson from a very fine local turner. His method is 1 hour per inch thickness. He also maintains that you can under boil, but not over boil. What you are looking for is a uniform temperature throughout the piece.

Thanks -- sounds like I was pretty much on point then.

[Reed Gray]

Dale Larson, who does a lot of madrone says 1 hour per inch of thickness, and then allow the blanks to come back to ambient temperatures in the water before removing. Where you are, sealing, and then putting in a cool damp place (air conditioning actually pulls water out of the air) to dry. Sealing might be necessary as well. The paper bag inside a plastic bag might be necessart (change out the paper bags daily, dried out bags can be reused). A lot depends on the wood as well.

robo hippy

[Jeffrey J Smith]

Rob - I use the '1 hour per inch of thickness' rule as a minimum. When I'm going to rough out blanks that I know will need boiling (madrone or fruit woods, mostly) I set aside a whole day. I get my boiling pot all setup and heating up before I start roughing out blanks. By the time the first one is roughed out and the coring starts, the water's at a slow boil. I just keep on chucking in cored blanks as I get them done. I've got a 120 Qt. stock pot that I use, so it will hold a lot of blanks.
If I need room in the pot, the first ones in get pulled from the pot and set in a cold water quenching tub for a few minutes, then stacked on the shop floor to dry. The pot keeps on boiiing as long as I've got blanks to rough and core out. When I'm done. I clean up the huge pile of shavings while the boiling goes on untril the last one in has been boiled for a couple of hours. Then it's out of the pot, quenched, then stacked to dry.
When the surface has dried pretty well - a couple of days usually - they get stickered and stacked rim down on the shop floor.
I have, on occasion, left them in the pot until it cools (overnight usually) but, it seems like everytime I do that The blanks get a bad case of the mold soon after. When I put them out hot to cool in the ambient temp I have much less of a problem with mold. Not entirely sure the two are related, but, call me superstitious, I don't leave them in the pot to cool anymore...

I've read Reed's process of wrapping the rims in stretch wrap and plan to give it a try when I'm roughing next - sounds like a great tip to keep the rims intact.

One critical thing to avoid cracks in the rim - make sure you round off the edge of the rim. Leaving a sharp edge to the rim pretty much ensures you'll get cracks since the sharp edge is much thinner than the rest of the wall, it will dry much faster and viola, cracks galore.


A few years ago, the neighborhood kids got brave and gathered around the pot to ask what I was doing. They looked in and saw the blood red extractives from the madrone I was boiling and I became an instant urban myth - the guy that boils 'unknown', stinky meat in his driveway (probably road kill). Maybe I'm just sensitive, but it seems like some of them have had a whole new respect for me since then...

[Reed Gray]

I don't think I have ever done twice turned bowls. I would think the plastic would be added protection for the rim. Let me know.

robo hippy

[Peter Blair]

I live in a much much wetter climate and usually boil all my rough turned bowls although I have been experimenting with just Anchorsealing Maple with mostly success. I started boiling following the protocol of Steve Russel http://www.woodturningvideosplus.com...reen-wood.html
I do get quite a lot of mould but it seems if I cool them quickly in a cold water bath I have less problems.
One issue that is seldom included is that the whole bowl needs to be under the water so ensure even boiling. I accomplish this with a weight and early on discovered that wood can catch on fire under water if there is a hollow and all the water boils out of the hollow.
Here's a shot of what happened to one of my pieces.
burnt.jpg
In the end i was lucky enough to save it. I now put a small piece of galvanized wire mesh in the bottom of my pot when I boil. ONe other thing to remember is that the rough turned bowl will expand and if it is a fairly tight fit in your boiling pot could potentially cause an explosion. Make sure that the bowl is at least an 1" smaller in diameter than the inside of your boiling pot.

[Reed Gray]

Not all woods need to be boiled. Madrone warps insanely, so if you want some thing twice turned, that is the only way to accomplish it with this wood, or any other wood that warps beyond the 10% rule. It will/can change the color of the wood a bit also. I have a friend who does large madrone hollow forms and he steams them because they are too big to fit into any pot.

robo hippy