If you don’t happen to have a traditional stone-floored domed clay oven on hand, it can be surprisingly challenging to make a pizza that’s truly excellent. Your domestic oven does a reasonable job, but doesn’t really get hot enough. Even a specialist pizza oven such as [Yvo de Haas]’ Ooni doesn’t quite do the best possible, so he’s upgraded it with the SpinMeister — a system for precise timing of the heat, and controlled rotation of the cooking stone for an even result.
The spinning part is handled by a stepper motor, driving a hex shaft attached to the bottom of the stone through a chuck. The rotating bearing itself is from an aftermarket stone rotator kit. The controller meanwhile is a smart 3D printed unit with a vacuum-fluorescent display module, powered from an Arduino Nano. There’s a motor controller to handle driving the stepper, and an MP3 module for audible warning. It’s all powered from a USB-C powerbank, for true portability. He’s produced a video showing it cooking a rather tasty-looking flatbread, which we’ve placed below. Now for some unaccountable reason, we want pizza.
Summer has settled upon the northern hemisphere, which means that it’s time for sweet, sweet strawberries to be cheap and plentiful. But would you believe they taste even better in freeze-dried format? I wouldn’t have ever known until I happened to get on a health kick and was looking for new things to eat. I’m not sure I could have picked a more expensive snack, but that’s why we’re here — I wanted to start freeze-drying my own strawberries.
While I could have just dropped a couple grand and bought some kind of freeze-drying contraption, I just don’t have that kind of money. And besides, no good Hackaday article would have come out of that. So I started looking for alternative ways of getting the job done.
Early on in my web crawling on the topic, I came across this Valley Food Storage blog entry that seems to have just about all the information I could possibly want about the various methods of freeze-drying food. The one that caught my eye was the dry ice method, mostly because it’s only supposed to take 24 hours.
Here’s what you do, in a nutshell: wash, hull, and slice the strawberries, then put them in a resealable bag. Leave the bag open so the moisture can evaporate. Put these bags in the bottom of a large Styrofoam cooler, and lay the dry ice on top. Loosely affix the lid and wait 24 hours for the magic to happen.
I still had some questions. Does all the moisture simply evaporate? Or will there be a puddle at the bottom of the cooler that could threaten my tangy, crispy strawberries? One important question: should I break up the dry ice? My local grocer sells it in five-pound blocks, according to their site. The freeze-drying blog suggests doing a pound-for-pound match-up of fruit and dry ice, so I guess I’m freeze-drying five entire pounds of strawberries. Hopefully, this works out and I have tasty treats for a couple of weeks or months.
Preparation
In order to make this go as smoothly as possible, I bought both a strawberry huller and a combination fruit and egg slicer. Five pounds of strawberries is kind of a lot, eh? I’m thinking maybe I will break up the ice and try doing fewer strawberries in case it’s a complete failure.
I must have gotten rid of all our Styrofoam coolers, so I called the grocery store to make sure they have them. Unfortunately, my regular store doesn’t also have dry ice, but that’s okay — I kind of want to be ready with my cooler when I get the dry ice and not have to negotiate buying both while also handling the ice.
So my plan is to go out and get the cooler and the strawberries, then come back and wash the berries. Then I’ll go back out and get the dry ice and then hull and slice all the berries. In the meantime, I bought some food-safe desiccant packets that absorb moisture and change color. If this experiment works, I don’t want my crispy strawberries ruined by Midwestern humidity.
Actually Doing the Thing
So I went and bought the cooler and the strawberries. They were $2.99 for a 2 lb. box, so I bought two boxes, thinking that a little more poundage in dry ice than berries would be a good thing. I went back out to the other grocery store for the dry ice, and the person in the meat department told me they sell it in pellets now, in 3- and 6-lb. bags. So I asked for the latter. All that worrying about breaking it up for nothing!
Then it was go time. I got out my cutting board and resigned myself to hulling and slicing around 75 strawberries. But you know, it really didn’t take that long, especially once I got a rhythm going. I had no idea what the volume would be like, so I started throwing the slices into a gallon-sized bag. But then it seemed like too much mass, so I ended up with them spread across five quart-sized bags. I laid them in the bottom of the cooler in layers, and poured the dry ice pellets on top. Then I took the cooler down to the basement and made note of the time.
Since I ended up with six pounds of dry ice and only four pounds of strawberries, my intent is to check on things after 18 hours, even though it’s supposed to take 24. My concern is that the strawberries will get done drying out earlier than the 24-hour mark, and then start absorbing moisture from the air.
Fruits of Labor
I decided to check the strawberries a little early. There was no way the ice was going to last 24 hours, and I think it’s because I purposely put the lid on upside down to make it extra loose. The strawberries are almost frozen and are quite tasty, but they are nowhere near depleted of moisture. So I decided to get more ice and keep going with the experiment.
I went out and got another 6 lb. of pellets. This time, I layered everything, starting with ice in the bottom and ending with ice on top. This time, I put the lid on the right way, just loosely.
Totally Not Dry, But Tasty
Well, I checked them a few hours before the 24-hour mark, and the result looks much the same as the previous morning. Very cold berries that appear to have lost no moisture at all. They taste great, though, so I put them in the freezer to use in smoothies.
All in all, I would say that this was a good experiment. Considering I didn’t have anything I needed when I started out, I would say it was fairly cost-effective as well. Here’s how the pricing breaks down:
28-quart Styrofoam cooler: $4.99
4 lbs. of strawberries: $5.99
12 lbs. of dry ice at $1.99/lb.: $24
a couple of resealable bags: $1
Total: $36, which is a little more than I paid for a big canister of freeze-dried strawberries on Amazon that lasted maybe a week. If this had worked, it would have been pretty cost-effective compared with buying them.
So, can you freeze-dry strawberries without a machine? Signs still point to yes, but I’m going to go ahead and blame the Midwestern humidity on this one. You can bet I’ll be trying this again in the winter, probably with fewer berries and smaller cooler. By the way, there was a small puddle underneath the cooler when it was all said and done.
Have you ever tried freeze-drying anything with dry ice? If so, how did it go? Do you have any tips? Let us know in the comments.
Despite the name, so-called “instant” noodles still need to sit for a few minutes before they’re actually ready to eat. Most people would likely use a simple kitchen timer to let them know when it’s time to chow down, but this unique mechanical timer uses the weight of the noodles themselves to power a timing mechanism.
The timer acts in much the same way that a pendulum clock would, in that a weight provides the energy to drive the clock’s mechanism which releases that energy in discrete steps. Besides a few metal parts and some magnets, the majority of the clock is 3D printed with a small platform on the side where the noodles rest. As the platform falls the weight drives the clock mechanism which will finally alert the user when they finish their descent three minutes later with the help of a small bell. There’s even an analog display which shows the number of minutes remaining before the noodles are ready to eat.
As far as single-purpose kitchen appliances go, this is one that we might find ourselves sacrificing some counter space for not only for the usefulness but also for the aesthetic appeal of the visible clock movements and high-quality design. It could even go beside the automatic ramen cooker for when we’re too busy (or lazy) to even boil the water for instant noodles ourselves.
Do you like your cup of tea to be cooled down to exactly 54 C, have a love for machining, and possess more than a little bit of a mad inventor bent? If so, then you have a lot in common with [Chronova Engineering]. In this video, we see him making a fully mechanical chime-ringing tea-temperature indicator – something we’d be tempted to do in silicon, but that’s admittedly pedestrian in comparison.
If you’ve never considered roasting your own coffee at home, you may be surprised to learn that it can be done in a few minutes with a regular popcorn popper and not much else. After all, you only really need two things to roast coffee: heat, and constant agitation to distribute that heat evenly. While the popcorn popper provides both, it’s easy to end up with semi-uneven roasts, probably because the beans are mostly just spinning around and not being tossed as well as they could be. Eventually, one might want a more advanced machine, and that’s where something like [Larry Cotton]’s latest wobble disk roaster can step in.
For starters, this machine roasts more beans than the average popcorn popper in a single throw — the maximum is 350g, or just over three-quarters of a full pound, which is way more than the average popcorn machine will hold. It essentially consists of a heat gun pointed upwards at a sieve full of green coffee beans that are being constantly pushed around by a motorized wobbling disk. As the heat blows, the large metal disk does figure eights through the beans, keeping the heat nice and even. So where does the red ball come in? It’s at the bottom, keeping the flying bean skins (chaff) from entering the heat gun’s fan motor.
Toward the end of the short video after the break, you’ll see a diagram showing all the parts of this roaster. If that’s not enough for you, here’s a build guide for a previous wobble disk roaster (PDF) that should be quite helpful in building either version.
If you want to see some of Larry’s previous machines, we’ve got ’em. And then you can let Hackaday Editor-in-Chief [Elliot Williams] tell you all about roasting at home.
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