scorched side in bender

[peter havriluk]

John, the location of the thermocouple warrants some thinking. I certainly wasn't worried about where to put it, so long as it was in the bundle of slats/parchment/wood. I think I want to put it right beneath the blanket, which I may not have done. Maybe you've offered an answer. If I'd put the thermocouple beneath the wood, between the wood and the inner slat, I can see how I'd have a path to overheating the wood, and I do recall the thermocouple temperature being slow to rise when the blanket was powered up, but I wasn't considering whether the slow rise was a sign of something gone amiss. What could go wrong? I had a digital controller!

Thanks!

[peter havriluk]

Dave, the 'Windex' I used wasn't that brand name, but it looked like all the blue watery stuff we associate with that name (like Kleenex). When I bought my shop jug of the stuff I made sure that ammonia was listed on the ingredients. I don't know whether ammonia is commonly used or not commonly used, but I found mine the first place I looked.

[peter havriluk]

Bent the second side this morning, as much like on the scorched one as I could make it, except for the location of the thermocouple, which I put on the outer side of the heat blanket. World of improvement. I think I learned a lesson about locating thermocouples. Heat came up much faster on the thermocouple line, too, this time.

Thanks, everybody!

Glad to hear it.

[Carl Dickinson]

I bent some afrormosia sides where a digital thermometer was in an aluminum tube between the wood and the blanket. That made a nice black line across the side that wouldn't sand out all the way. I had to shade the the sides in the initial nitro coats to mask it. So now I put the thermometer outside of the blanket under the top slat.

Dave, the idea for using windex comes from John Hall over on kitguitarsforum. Some details there and OLF.

[peter havriluk]

After deciding that nothing more was to be gained by procrastinating, today I bent a new set of sides, same species as I scorched. This time I put the thermocouple probe between the heat blanket and the wood. I made a sandwich of aluminum (2024-T3) slats, heat blanket, wood wrapped in baker's parchment paper. First side picked up a few impressions from the heat blanket, the second none. The difference was putting a paper towel layer atop the wood, and then putting the wood in the sandwich.

So, a question about parchment paper to avoid direct contact between wood and either blanket or aluminum. Necessary? Substitutes? Did if stumble into a valid substitute for the parchment in the paper towels? Has anyone else encountered scorching when using parchment paper between wood and the other parts of the bending array?

Thanks, folks. I wish I knew the recipe before I started cooking.

[Carl Dickinson]

I've heard that parchment paper from the market can have silicone in it so I quit using it. I've had good luck using brown packaging paper cut to 6"x36" strips which are quickly dipped thru a tray of water (I'm going to try windex tomorrow). The sandwich used last time was - steel slat, paper, wood, paper, thin aluminum slat, blanket, steel slat. Worked fine with mahogany, quilted maple, and walnut. Tomorrow's bends will be with afrormosia and bocote both of which caused me problems in the past.

[peter havriluk]

Carl, so there's a third metal slat in the sandwich, the third one interposed between the heat blanket and the paper and wood? That can be arranged. I have access to an infinite supply of 2024-T3 .020 aluminum sheet.

And the brown paper sounds like something i can easily find.

Please speak up after the next bending party.

Thanks!