Rocket Stove

Maybe you’ve stored 100 pounds of wheat kernels, 75 pounds of beans, barrels of water and you’re all set for whatever municipal unreliability may bring. One question:

How will you cook the food you’ve stored?

In Food Storage and Refried Beans, back in April 2009,  I determined that to cook 100 pounds of beans would take about 4.7 gallons of white gas (Coleman fuel). Assuming the rest of a typical day takes a little less gas, you would still have to store about 10 gallons of gas to service that much food. While this is doable, it is certainly a hazardous amount of fuel. My personal solution is my own take on the Rocket Stove.

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We have a wood burning fireplace, but it is not set up for cooking. However, we keep wood around for the cold winter nights. Obviously, mankind has cooked on wood basically forever. So, obviously it is possible. I was introduced to the rocket stove developed by Aprovecho, which is intended to reduce fuel consumption by more efficiently transferring the wood’s energy into the cookpot, reduce air smoke and soot inhalation by combusting more efficiently, and improve burn safety. They have ten design principals, summarized:

  1. Insulate around the firebox. I do this by using insulating kiln brick (about 0.65 g/cm3).
  2. Place an insulating short chimney directly above the fire. Mine is about 9 inches high, made by two races of insulating brick.
  3. Heat and burn (just) the tips of the sticks. The shortness of the firebox accomplishes.
  4. Heat is regulated by the amount of fuel. I have no damper, which their research shows is not effective.
  5. Maintain a good fast draft through the fire. This is accomplished both with the chimney and a recovered steel grate that creates an air channel under the burning fuel.
  6. Too little draft makes excess smoke. See principle 7.
  7. The opening, size of spaces, and chimney should all be about the same size. Specifically they recommend a 12 cm square opening (4.75 in), which is about 3.5 inches, and is probably slightly too small.
  8. Use a grate under the fire. See principle 5.
  9. Insulate the heat flow path. My entire structure is made of insulating kiln brick.
  10. Maximize heat transfer to the pot with properly sized gaps. I have not yet begun this phase of development.

For an initial design I used twelve insulating kiln bricks. Four make a floor—insulated enough, I think, to be used on a wooden stand. Two were cut into plugs to make the sides complete, and the remainder were stacked to make a square chimney and burn chamber. The burn chamber as seen through the chimney is filled with embers.

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I scrounged and bent a wire rack to make a grate that retains a channel for air flow under the combustibles.

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On top I used four small stones to make a burner. This is very much the wrong design for quickly heating water, but it worked for a test run.

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Actually, it worked for three test runs. Yesterday we boiled water for tea.

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This morning the kids helped make oatmeal on it. This evening I caramelized onions on it while grilling burgers.

My impression is that this device is the bee’s knees! The smoke was minimal (not as minimal as I would have liked, but largely avoidable). The amount of wood burned was about 4 linear feet of thumb-diameter sticks. The stove is stable, even with my crummy burner. I think it would make a nice patio fireplace for autumn evenings. Small, but controlling the smoke makes it much more pleasant to be around.

I do look forward to improving it. It is a pain to move, since it is about 45 pounds and doesn’t hold itself together. It is too low to cook on comfortably. Its heat transfer are near the pot is not well sized. This all requires work. I would also like to measure the efficiency of the stove. Always more fun to have!

Very Bad Food

Welcome to Ink of Park’s new home. I’m kicking off this site transition with another first. My wife and I recorded our first podcast under nom de plume Thistle and The Bear. Enjoy it!

You can listen in-browser (below) or download the file.

 

Hot-Smoked Salmon

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This afternoon I made hot-smoked salmon in my father’s MasterBilt smoker. The Web did not provide me with good resources on smoking salmon in a MasterBilt. Or rather, it provided many different and vague recipes. My result was excellent but not perfect. This article details exactly what I did and exactly what I plan to do the next time.

My target dinner time was 6 pm. I started with a 1.5 lb skinless salmon fillet about 1 inch thick at the thick part, still partly frozen, and 4 ounces of dry hickory chips. At 11 am I made a brine with 1 quart (4 cups) of tap water, 3/8 cup of iodized table salt, and 3/8 cup of packed light brown sugar.

The fish soaked for 90 minutes in the brine. I removed the fish from the brine, and dried both sides with paper towels. I placed the fish on a cooking-spray coated double-layer of aluminum foil. The fillet air-dried for 30 minutes, until 1 pm. I put the fish in the smoker, and then turned the smoker on to 210 F. The smoker started producing smoke with residual chips after about 20 minutes. At 1:30 I put in about half the smoked chips, and at 2:00 I put in the remaining chips.

I left the fish completely alone until 4 pm—at which time the fish had been cooking for 3 hours. I brushed the fish with maple syrup, about two teaspoons. I tested the temperature and at the thickest part it was already up to about 170—well over the target temperature of 165 F. Dinner was still two hours away, so I dropped the temperature to 140 F and left the fish in the cooker until about 5:45 pm.

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The result was beautiful to look at, and smelled enchanting. The thick parts of the fish, oddly, were overcooked and dry—a texture like papier mache. The thin parts were moist and rich. My guess is that the brine did not penetrate and protect the inner parts of the fish. Of course it was obviously overcooked too.

You can see the dark smoky coating on the fish. The inside stays the pale color of poached salmon. The flavor was excellent. My 5 year old and 8 year old both ate it and wanted more. They seemed to like the smoke and the slightly sweet coating. My wife and I enjoyed it too, so the meal was a success. Next time it will be better.

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Next Time

  • Start with fully thawed salmon.
  • Make only two cups of brine, and use a freezer bag to brine the fish.
  • Start brining the night before.
  • Use 4 oz hickory chips (same as this time)
  • Give the fish about an hour to dry after pulling from the brine
  • Put fish in cold cooker at 2 pm (4 hours before serving)
  • Cook with MasterBilt set at 210 degrees F.
  • Put first load of wood chips in once temperature reaches near the set point, about 30 minutes.
  • Put the second load of wood chips in after the smoke stops, about 3:30 pm.
  • Go running (optional)
  • At 5 pm, glaze with about 1 tablespoon of maple syrup
  • At 6 pm, remove and serve immediately

Barbecued Ribs and Smoke Metrology

I made smoked ribs yesterday and tested out a new measurement system based on an Arduino, data logger shield, and a Sharp GP2Y1010 dust measurement unit. I didn’t have a long enough cable to get the smoke measurement unit inside the smoker, so I put it in my own contained pod above the smoker. By “pod” I mean the red re-purposed steel can on top.

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The smoke extension pod has a port for sensor access and an adjustable damper. You can see the ribbon cable coming from inside the can to the data logger.

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The sensor access port is on the bottom front of the picture below.

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The smoke sensor, shown below, has some very small deposits around the sensor hole—the big hole in the center. In addition, I used the RIMU to log the temperature inside the smoker.

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The temperature, oddly, was much too high. It is supposed to be 225F, but I appear to have set it at 265F. Perhaps there is a problem with the RIMU, but more likely there is a problem with the built-in sensor. The error in temperature control did not hurt the ribs, they were excellent. Further investigation is needed.temp_in_plot

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The smoke voltage measured with the Sharp GP2Y1010 appears to distinguish between noise (between 0 and 1 volt) and total saturation. It is, nevertheless, a pretty good indicator of when smoke was applied. I loaded the smoker with chips at 10 am, and there was no smoke noticeable until 10:30 am. The full load of chips produced smoke for about 1/2 hour and then stopped almost completely. I put in a second, smaller, dose of chips at 11:30, which produced about 20 minutes of smoke from 11:45 until shortly after 12:00.

The period of time from about 14:30 until 15:30 is unexplained. I would guess that the ribs were slowly dripping, and each drip would burn and generate a short dose of smoke. It started at a time when I had moved the smoker onto the porch to avoid threatening rainstorms, and perhaps an angle changed. The smoker was shut off briefly, which explains the temperature drop around 14:20. The pattern of increased smoke does appear to match the temperature cycle.

The amount of smoke, or at least its duration, seems to relate well to the amount of chips. Smoke seems to start about 20 minutes after chips are applied, and lasts for up to 30 minutes.

Better Bread from the Bread Machine

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We have a Cuisinart convection bread machine (CBK-200) that was a given to us for Christmas one year. It is an attractive and well-featured machine, but I haven’t had much loaf success with it. We have had bread machines in the past. The Cuisinart tries to produce a loaf which is horizontal, like a loaf from a conventional pan. Overall Cuisinart’s design was not a good compromise. The wide loaf pan accumulates clumps of unmixed flour on the edges. These remain in the baked loaf, and are inedible and unsightly.

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The loaves also come out, usually, concave on the top. They rise high then collapse to produce an ugly loaf with a flavorless crust. I set out to improve on this using 3-factor, 2-state screening design to study the influence of sugar, water, and yeast. Foolishly, I started with the Cook’s Illustrated recipe from the mid 90’s, rather than starting with the Cuisinart book’s recipe.

I hypothesized that our high altitude (1 mile above sea level) was the cause. My results with the Cook’s Illustrated recipe were like the abhorrent results from the Cuisinart book (see results ). I used the results of the screening experiment for guidance by extrapolating the fitted equation along the curve of steepest ascent. Unfortunately, I had two different extrapolation curves–one for height of the loaf at its center and another for the height of the loaf at its edges. One curve said to add more yeast, the other said to add less yeast. So, I read more of the advice available online. Probably I should have spent more time reading at the start. For the sunken loaf problem all advice was consistent: add less sugar, less water, and less yeast, and maybe add more salt.

I used my curve which predicted less yeast to extrapolate the amount of water, and yeast, and sugar. The result of that extrapolation was almost the same amount of sugar and the same amount of yeast recommended in the Cuisinart book. The Duh! moment. However, my prediction wanted less water, much less. The Cuisinart recipe wanted 1.42 flour:water by weight, but my extrapolated recipe wanted only 1.96 flour:water by weight.

I am not done with the experiment yet. Because I autonomously concluded that I should use the same amount of salt and yeast as the Cuisinart recipe, I believe that those factors do not need further exploration. The flour:water ratio, on the other hand, is worth exploring.

Flour and Water

I am horrified by the lack of consistency in the specification of flour weight and volume. One thread indicates that the weight of a fixed amount of flour will change by about 2% due to humidity variation. I’m more than satisfied with 2% accuracy. Measurement by volume, on the other hand, may vary by over 10%.

Because of this variation you would think that the assumed weight of a cup of all purpose flour would be a standard. But no. Consider these sources:

4.25 oz King Arthur
4.375 oz USDA
4.625 oz Gold Medal
4.7 oz joyofbaking.com
4.75 oz preparedpantry.com
5 oz Artisan Bread in 5 Minutes
5.5 oz Cook’s Illustrated Rustic Italian Bread (bread flour ~5% denser)

When a recipe says “one cup of flour”, it is talking about somewhere between 4 and 5.5 oz, a variation of +/-15%. The people worrying about the 2% variation due to humidity are clearly insane, since unless the recipe specifies, no recipe reader has much better than 15% accuracy just understanding the author. I use 4.25 oz/C in my recipes.

Since nobody seems to publish actual data on the net, I will. I used dip-level-pour measurement for 17 trials. The sample mean is 4.76 oz, and the sample standard deviation is 0.17 oz.

Num oz Num oz
1 5.00 9 4.50
2 4.80 10 4.65
3 4.70 11 4.65
4 4.80 12 4.75
5 4.90 13 5.05
6 4.65 14 4.80
7 4.50 15 4.80
8 4.65 16 5.05
17 4.75
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2 The Recipes

Add the ingredients in the order listed. Set the machine for 1.5 lb loaf, with a light crust. Note: my recipe developed at 1 mile above sea level.

Mine CI Cuisinart
6.5 fl oz 10 fl oz 9 fl oz water, fl. oz.
1 Tbsp 1 Tbsp 2.33 Tbsp oil, tablespoons
1 tsp 1 tsp lemon juice
2 tsp 3 tsp 2.25 tsp granulated sugar, teaspoons
1 tsp 1 tsp 1.125 tsp salt, teaspoons
12.75 oz (3 C) 12.75 (3 C) 3 C flour, C
1/4 C 1/4 C 3 Tbsp nonfat dry milk
1.25 tsp 2 1/4 tsp 1.5 tsp instant yeast

I have tried recipes with 6.5, 7, and 7.5 fl oz of water. Both 6.5 and 7 produced nice loaves, but 7.5 again produced a saggy loaf. This provides a fairly contained range to consider for a response surface method. Though perhaps the next experiment will include some whole wheat.

Sourdough Chowder Bowls

In San Francisco, on the wharf, you can buy a hollowed-out loaf of sourdough bread, filled with New England style clam chowder. You can buy it from street vendors, or sit down in a restaurant and eat it. Sourdough and San Francisco go together. I love the bowl, chewy, flavorful, damp from the chowder. I even like the chowder, which is pretty much like what you get from a can. Unfortunately, Albuquerque does not have a wharf on the Rio. What to do when I want a chowder bread bowl on a cold late autumn day.

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I made them today, to moderate success. Two weeks ago I made them to miserable failure, having forgotten the salt. The recipe is simple, the challenge is in the baking. I bake in a convection oven, but the process is almost the same without convection. I put the boules in a pre-heated covered Pyrex baking dish at 425 for 15 minutes then uncover the dish and lower the temperature to 325 for between 20 and 35 more minutes. I spray the boules with water before putting them in the dish, to help the crust develop.

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The crumb is dense, the crust is chewy, the taste sour but not overpowering. The chowder, from a can, hearty.

  • 3 cups of flour (4.4 oz each, by weight)
  • 1 tablespoon salt
  • 1 cup sourdough starter
  • 1/2 cup water, around 100 degrees F