A 46-oz Steinfeld's pickle jar painted black with one line masked out for viewing the food through the side: a great bean pot in the #solaroven! Frijoles de la olla del sol. I could have used a traditional bean pot (olla de barro) as long as it's dark colored on the outside, but I don't have one, and I did have this.
Looks kinda weird but they turned out extremely tender with no split #beans or tough skins, and the broth is delicious (I brined the beans overnight first). Also no electricity, gas, or wood, and no stirring or checking needed. Dry beans are the cheapest high protein food (#vegan and otherwise!) , but few people cook them because it takes so long and uses a lot of energy. A great choice for #solarcooking to #feedtheworld. #diy #solar #cheapfood #solarpunk
@ordinoides Very interesting indeed. I love beans, cook them in big batches, and freeze them six cup portions.
Did you note the maximum temperature reached by the product during the process?
@shuttersparks
Well the beans were at 212F because I saw the water boiling vigorously, they can't get hotter than that in this device because it's not pressurized. I took a picture of the thermometer at 199 F but of course the temp started dropping as soon as I removed it from the oven and took the lid off. I was concerned at first that I wouldn't be able to get the beans hot enough to destroy the phytohaemagglutinin, which is the toxin a lot of people know is present in kidney beans, but it's actually in all New World beans. It breaks down at around 190 F, so these are definitely safe to eat.
I have seen the outside of the cooking vessel get up to 307 F when I was baking bread.
@ordinoides Okay, gotcha. That's plenty hot. I was thinking food safety and wondering if this method was a sort of sous vide or "sun tea" approach that can not only fail to kill pathogens but encourage their growth.
So yeah, nevermind. No worries. :-)
@shuttersparks
Yeah food safety is a huge concern for me too! When I did this project with students I harped on the "Danger Zone" of food temps a lot. Perishable food (meaning it's wet, is nearly neutral pH, and doesn't contain antimicrobials) needs to get above 140F in less than 2 hours or you're taking a big risk. Good thing kids LOVE using the infrared thermometer "guns" to check the temperature, lol.
@ordinoides Hah, yeah. I'm a retired engineer, now working as a chef, so I tend to mix science and food. My IR gun gets plenty of use but it's also useful to compare with an ordinary accurate thermometer when possible. Emissivity is a thing, especially with metals, but I'm sure you know that.
@shuttersparks yes! I actually didn't know the technical term for it- had to look up "emissivity" (TIL, thank you!) - but I've noticed many times that the ir thermometer does weird things on shiny and clear surfaces. Like it can measure the temp of a dark colored object though clear polyfilm, but NOT through clear acrylic, whoa! Good thing the same surface characteristics needed for solar cooking (matte black) also are good for ir thermometer use, for the most part.
@ordinoides Yes, it's a big problem that can throw your readings way off, as you noticed.
Your IR gun probably has an adjustable setting for emissivity. I've found that in practice it's a hassle and not real useful. It is useful in certain settings like if you are going to do a bunch of readings of the temp of the outside of a particular stainless steel pot. Then it's worthwhile to calibrate. Or if I'm welding / heat treating steel, then I recalibrate. (My gadget works up to 1,800 F.)
But for random kitchen use I just leave it set to 0.96 and am aware that if I read a metal object the temp is going to be off. Some materials like stainless steel and galvanized steel are especially bad. Polished copper's emissivity is so low it's not worth trying to measure it accurately.
The above is not a recommendation, just the way I use mine.
Here's a chart with some possibly useful numbers to plug into your gun. https://www.thermoworks.com/emissivity-table/
@ordinoides Yup. That's good enough.
To belabor the topic a bit more, and in case others are reading too, I'll mention one more thing.
Looking at the table of material emissivities, it might seem like many of the numbers are approximate or have a range of values. That's not useful if you want accuracy. The reason for the approximations is that emissivity of a material depends on the composition of the material and its surface finish. So stainless steel -- which alloy?, is it a brushed finish?, sanded?, polished?, corroded?, dirty? These all affect emissivity, sometimes in a major way.
But if you have a particular case then you can measure emissivity yourself. Say you have a big stainless cauldron. Fill it with water. Heat the water to some temperature you can measure accurately, say around 160F. Shut off the heat source and let it stabilize a minute. (Avoid airflow, breezes, wind, etc. because stainless is a poor heat conductor.) Then measure with the IR gun and fiddle with the emissivity setting until it reads the temp accurately. Now you're calibrated and you know the emissivity of that material given it's current state of finish, corrosion, dirt, etc.
Note that one could do this at room temperature but the IR gun will be somewhat more accurate if the temp of the material is above ambient and closer to the temperatures you expect to measure.
@shuttersparks
Neat! Yeah I think I will just leave it at .96 or whatever the default setting is, because I'm mostly measuring food or painted dull black surfaces, and those are close to .96 already. This is really cool to see though. Acrylic has emissivity of .94, which means that my temp checks on the outside of the lid are close to accurate for the temp of the acrylic itself. Pics of reading the outside temp on acrylic and inside temp on painted black cooking vessel, taken seconds apart when ambient temp about 75 F, about 5 minutes after putting the pot in the #solaroven.