Torch burning advice

[Donald Pratt]

I’ve been trying to use a propane torch to embellish maple bowls and platters and I’m having a heck of a time. On the first piece, a small plate, the wood warped like crazy. On my next piece, a bowl, I turned the outside and decided to burn it before hollowing. I thought that might limit the warping, but instead it developed some significant cracks. I went ahead and hollowed it anyway and think it looks OK, but it’s definitely not what I was going for.

Both blanks were many years old and completely dry. Anyone have any tips for successfully burning a bowl or platter? I found a YouTube video by Sam Angelo, but warping wasn’t even mentioned.

Thanks in advance.

 

[Bill Boehme]

Can you describe what you were trying to achieve?

This might not be the effect that you want, but I have used MAPP gas to torch a lidded vessel turned from ash in a class with Jimmy Clewes. After torching I used a brass bristled brush to get rid of the loose charcoal dust. This process burns the softer early wood while not harming the late wood. Propane isn't hot enough because the burning needs to be done quickly. This wouldn't work with maple.

 

[Richard Coers]

Your comment, completely dry is a relative term in my opinion. An 8" cube is hardly every completely dry in the middle. Also there can be stresses in wood that will reveal very quickly with extreme heat from a torch. Some cracking in any torch treatment can happen, and most just brush off the char and get what they get. For best results I would only burn nearly complete work, with very even wall thickness and not much more than 1/4" thick. I would suggest you move the torch around and not concentrate on a small spot. Nick Cook has been doing these for decades.

View: https://www.youtube.com/watch?v=41x6CsGMV6w

 

[John Dillon]

I've used a standard propane torch to burn/highlight the open grain in ash, oak and some nondescript grain like is found in sweergum. I've also put a heavy burn on some oak and brass brushed the char prior to using a) gilt wax and/or b) acylic paints.
I believe the cracks or splits may be related to wood with too much moisture.

 

[Perry Hilbert]

Back when I first started turning, I "textured" several boxes and bowls by charring them on the outside and then scrubbing the soft char way with a wire brush. That sort of Spanish-Western, dark dark brown heavy pine furniture was in back then and it fit the style. I found that clear yellow pine looked the best with such treatment. The hard rings stood up against the burning and scrubbing with wire, while the soft areas between scrubbed away to a depth of about 3/32. Some of it took on a cord du roy appearance, with a medium tan between the dark, almost black rings standing proud. I don't recall what species of woods I tried, it needed to be something with a fairly uniform grain with enough space between rings to permit the wire to scrub away. As i recall, some woods did not texture because the rings didn't stand out. With the yellow pine, the first, I did that way to try to cover yup tear out. It worked wonderfully for that. I charred the wood to an even black all the way round, being careful not to let the wood catch fire. When it cooled off, I scrubbed it with a wire brush. End grain turning seemed to look better than side grain turning, because with side grain, there is wide grain on two sides with tight grain alternating on the other two sides..

 

[Tom Albrecht]

Can you describe what you were trying to achieve?

This might not be the effect that you want, but I have used MAPP gas to torch a lidded vessel turned from ash in a class with Jimmy Clewes. After torching I used a brass bristled brush to get rid of the loose charcoal dust. This process burns the softer early wood while not harming the late wood. Propane isn't hot enough because the burning needs to be done quickly. This wouldn't work with maple.

Good point-- all gas not being equal.

 

[Dave Landers]

On some pieces I've done, I've had success with a brulee torch (small butane torch from the cooking store). It is nice because it burns a small area at a time, so you can control the overheating. I've mostly burned the open pores of Ash, and the smaller flame allows me to "draw" that pattern.

Heat will dry the wood rather quickly (even "dry" wood has moisture and can be made "more dry"). So cracks are a potential problem. Depending on the wood, a smaller flame like the brulee torch can help with minimizing heated area. Or you might need a hotter flame (like MAPP torch @Bill Boehme suggests) to minimize the time the torch is on the wood. I'll also sometimes have a spray bottle of water set on the mister setting to help with moisture and cooling.

In any case, it takes experimentation and either a light touch or a quick touch. And the willingness to live with what you get. Sometimes when you burn wood you just get firewood

 

[Donald Pratt]

Can you describe what you were trying to achieve?

This might not be the effect that you want, but I have used MAPP gas to torch a lidded vessel turned from ash in a class with Jimmy Clewes. After torching I used a brass bristled brush to get rid of the loose charcoal dust. This process burns the softer early wood while not harming the late wood. Propane isn't hot enough because the burning needs to be done quickly. This wouldn't work with maple.

Thanks for the reply. I’ve seen others doing the early/late wood emphasis, but that’s not what I’m going for. I guess the best way to describe what I’m trying to get would be an ebonizing effect. I know I could get that with dyes or chemicals, but burning there’s just something about burning. Sorry, I know that’s not very helpful.

 

[Donald Pratt]

Your comment, completely dry is a relative term in my opinion. An 8" cube is hardly every completely dry in the middle. Also there can be stresses in wood that will reveal very quickly with extreme heat from a torch. Some cracking in any torch treatment can happen, and most just brush off the char and get what they get.

Thanks, Richard. Point taken about no wood ever being completely dry. In my case, the plate was from a 1” thick board that’s been sitting around the shop for a year or two and the bowl was from a 10x3 blank that’s at least 6 years old. I figured both would be about as dry as they’re going to get, and she shavings felt that way.
I hadn’t seen that video, but I read Nick’s article from the journal back in 2005. I don’t remember him mentioning warping and was really surprised how much that plate moved.

 

[Bill Boehme]

Wet wood and dry wood warp for different reasons. Wet wood warps due to shrinkage. Dry wood warps because there are internal stresses in the wood. The stresses are in equilibrium until some wood is removed and upsets the equilibrium. This causes the wood to warp and/or crack until internal stresses are once again in equilibrium.

 

[John Walls]

That must be why I hear/read everyone saying stabilize the wood, use CA. Next order I make, I will include some for sure. Unless there's something else suggested.
That, and a good moisture meter. Wagners good?

 

[Arkriver]

A moisture meter will not tell you how dry or wet wood is in the center of the piece, only on the outer edge. That is why a scale is often used and the weight noted over a period of time until there is no change in weight. Allyn

 

[hockenbery]

been sitting around the shop for a year or two and the bowl was from a 10x3 blank that’s at least 6 years old. I figured both would be about as dry as they’re going to get,

“as dry as it it gets” is totally dependent on the relative humidity and temperature of where the wood is kept.
Put dry wood in a humid environment it takes on moisture.

My drying room is kept at 50% RH and is usually warmer than 70F.
So “dry as it gets” for me is 9%MC.
Weighing is one way to determine “as dry as it gets” but you have to know the environment to know the MC.

Find the the value for your shop. In the table below.
My weather app say Ramona CA today is 60F and 60% of coarse the weather changes but for those values “as dry as it gets” is 11%.

 

[Richard Coers]

Can you describe what you were trying to achieve?

This might not be the effect that you want, but I have used MAPP gas to torch a lidded vessel turned from ash in a class with Jimmy Clewes. After torching I used a brass bristled brush to get rid of the loose charcoal dust. This process burns the softer early wood while not harming the late wood. Propane isn't hot enough because the burning needs to be done quickly. This wouldn't work with maple.

According to Bernzomatic, their propane torch burns at 3,600 in air and their Mapp-Pro burns at 3730.

 

[Bill Boehme]

According to Bernzomatic, their propane torch burns at 3,600 in air and their Mapp-Pro burns at 3730.

Those are the theoretical temperatures for the primary flame, but in reality the temperatures may be somewhat lower, especially for propane. Here is an excerpt from Gas Burners for Forges, Furnaces, & Kilns:



It's hard to say about MAPP gas (a mixture of methylacetylene and propadiene) since the only plant that manufactured it in North America shut down about a dozen years ago. What is available today are MAPP substitutes and each manufacturer has their own secret sauce. My guess is that the actual temperature difference between propane and today's MAPP substitute is greater than 130 °F.

 

[Donald Pratt]

Wow, thanks everyone for jumping in on this. Sounds like there’s no secret sauce, but there are some things to try - MAPP torch, brûlée torch, maybe other wood species, and lots of experimenting and making firewood. I also learned to never say I’m working with dry wood

 

[john lucas]

MAPP gas torches aren't necessarily hotter they simply provide more volume of heat so they heat things quicker. That being said I think what you need to get ebonized look is simply patience. Hold the torch further away and just pan across the surface and gently heat it. If you stay in one spot just a hair too long it will start to actually burn and char. It doesn't take long to turn wood brown, and a fraction longer and it turns black. Also if you have any sharp details, they heat up and turn black faster. If you have flutes the flames simply may not get down into the flute unless you have a small pointed flame.

 

[Bill Boehme]

MAPP gas torches aren't necessarily hotter they simply provide more volume of heat so they heat things quicker ....

Heat and temperature aren't the same thing. Saying "more volume of heat" is equivalent to saying higher temperature.

 

[Mike Zip Hamilton]

Bill, if one puts a single candle under a pot of water, it will raise the temperature of the water X degrees. Putting 20 of the same candles under the pot will deliver more BTU's (heat) to the pot raising the temperature of the water faster. I don't think heat and temperature measure the same thing.

 

[John Dillon]

Wow, thanks everyone for jumping in on this. Sounds like there’s no secret sauce, but there are some things to try - MAPP torch, brûlée torch, maybe other wood species, and lots of experimenting and making firewood. I also learned to never say I’m working with dry wood

Donald - attaching a pic of a Red Oak form recently given to me by Roberto Ferrer (Chicago Wood Turners Club). I burned the outside, heavy, using a standard propane torch, and lightly brass brushed the char from the grain. Used water based, (metallic colors) acrylic paints to give some color to the outside of the bowl. Tried to use flat brush strokes across the grain to keep the, black background, grain pattern open. Colors are a little more vivid than the picture shows. Walnut oil finish on the interior. You could also use india ink or black gesso as a background, but would miss out on the awesome grain patterns the burning and charring (light brushing) allows for. After this COVID-19 crisis subsides, then Roberto will finally get to see this too!

 

[John Dillon]

Should have mentioned I painted this after recently seeing a demonstration by Andi Wolfe at our club. Credits for painting techniques and ideas to Andi. You should take a look at some of her work for inspiration!