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.

Dry Ice Is Nice

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.

Main and thumbnail images via Unsplash

For all intents and purposes, photography here in 2024 is digital. Of course chemical photography still exists, and there are a bunch of us who love it for what it is, but even as we hang up our latest strip of negatives to dry we have to admit that it’s no longer mainstream. Among those enthusiasts who work with conventional black-and-white or dye-coupler colour film are a special breed whose chemistry takes them into more obscure pathways.

Wet-collodion plates for example, or in the case of [Jon Hilty], the Lumière autochrome process. This is a colour photography process from the early years of the twentieth century, employing a layer of red, green, and blue grains above a photosensitive emulsion. Its preparation is notoriously difficult, and he’s lightened the load somewhat with the clever use of CNC machinery to automate some of it.

His web site has the full details of how he prepares and exposes the plates, so perhaps it’s best here to recap how it works. Red, green, and blue dyed potato starch grains are laid uniformly on a glass plate, then dried and pressed to form a random array of tiny RGB filters. The photographic emulsion is laid on top of that, and once it is ready the exposure is made from the glass side do the light passes through the filters.

If the emulsion is then developed using a reversal process as for example a slide would be, the result is a black and white image bearing colour information in that random array, which when viewed has red, green, and blue light from those starch filters passing through it. To the viewer’s eye, this then appears as a colour image.

We can’t help being fascinated by the autochrome process, and while we know we’ll never do it ourselves it’s great to see someone else working with it and producing 21st century plates that look a hundred years old.

While this may be the first time we’ve featured such a deep dive into autochrome, it’s certainly not the first time we’ve looked at alternative photographic chemistries.

Weren’t we just talking about coffee-based sacrilege the other day? Here’s something to make the single-origin bean snobs chew their espresso cups: an artisan roastery in Helsinki is offering a coffee blend created by artificial intelligence called AI-conic. The idea, of course, is that technology will lighten the workload needed to produce coffee.

This is an interesting development because Finland consumes the most coffee in the world, according to the International Coffee Organization. Coffee roasting is a highly-valued traditional artisan profession there, so it stands to reason that they might turn to technology for help.

Just like with scotch whisky, there’s nothing wrong with coffee blends outright. Bean blends are good for consistency, when you want every cup to taste pretty much exactly the same. Single-origin beans, though, are traceable to one location, and as a result, they usually have a distinct flavor based on the climate they’re grown in.

If you’re new to coffee, blends are a nice, safe way to start out. And, interestingly, the AI chose to make the blend out of four different types of beans instead of the usual two or three, despite being tasked with creating a blend that would suit the palates of coffee enthusiasts. But the coffee experts agreed that the AI blend was “perfect” and needed no human intervention. We probably won’t be getting to Finland anytime soon, so if you try it, let us know how it tastes!

Do you like cold brew? How would you like to be able to brew some in just three minutes?

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.

The (long) video starts off with making a DIY bimetallic strip out of titanium and brass, which it pretty fun. After some math, it is tested in a cup of hot water to ballpark the deflection. Fast-forward through twenty minutes of machining, and you get to the reveal: a tippy cup that drops a bearing onto a bell when the deflection backs off enough to indicate that the set temperature has been reached. Rube Goldberg would have been proud.

OK, so this is bonkers enough. But would you believe a bimetallic strip can be used as a voltage regulator? How many other wacky uses for this niche tech do you know?

Thanks [Itay] for the tip!

Aluminum beverage cans are used for all kinds of drinks, but when it comes to wine there are some glitches. Chief among them is the fact that canned wine occasionally smelled like rotten eggs. Thankfully, researchers have figured out why that happens, and how to stop it. How was this determined? As the image above hints at, lots and lots of samples and testing.

What causes this, and why don’t other beverages have this problem? Testing revealed that the single most important factor was the presence of molecular sulfur dioxide (SO₂), a compound commonly used in winemaking as an antioxidant and antimicrobial.

It turns out that the thin plastic lining on the inside of beverage cans doesn’t fully stop molecular SO₂ from reacting with the surrounding aluminum, creating hydrogen sulfide (H₂S) in the process. H₂S has a very noticeable rotten egg smell, even in low concentrations.

Researchers discovered that if a canned beverage contained more than 0.5 ppm of molecular SO₂, a noticeable increase in hydrogen sulfide was likely to be present within four to eight months. The problem is that since most wines aim for around 0.5 ppm of SO₂, the average can on wine sitting on a shelf will have a problem sooner rather than later. The more SO₂ in the wine (reds tend to contain less, whites more), the worse the problem.

Simply increasing the thickness of the plastic liner is an imperfect solution since it increases manufacturing costs as well as waste. So, researchers believe the right move is to use a more durable liner formulation combined with a lower SO₂ concentration than winemakers are usually comfortable with. Unlike bottles, cans can be hermetically sealed which should offset the increased oxidation risk of using a lower concentration of SO₂. The result should be wine as a canned beverage, with a shelf life of at least 8 months.

The research is published here and gives a great look at just how one approaches this kind of scientific problem, as well as highlighting just how interesting the humble aluminum beverage can really is.

Battery technology is the major limiting factor for the large-scale adoption of electric vehicles and grid-level energy storage. Marginal improvements have been made for lithium cells in the past decade but the technology has arguably been fairly stagnant, at least on massive industrial scales. At smaller levels there have been some more outside-of-the-box developments for things like embedded systems and, at least in the case of this battery that can recharge itself, implantable batteries for medical devices.

The tiny battery uses sodium and gold for the anode and cathode, and takes oxygen from the body to complete the chemical reaction. With a virtually unlimited supply of oxygen available to it, the battery essentially never needs to be replaced or recharged. In lab tests, it took a bit of time for the implant site to heal before there was a reliable oxygen supply, though, but once healing was complete the battery’s performance leveled off.

Currently the tiny batteries have only been tested in rats as a proof-of-concept to demonstrate the chemistry and electricity generation capabilities, but there didn’t appear to be any adverse consequences. Technology like this could be a big improvement for implanted devices like pacemakers if it can scale up, and could even help fight diseases and improve healing times. For some more background on implantable devices, [Dan Maloney] catches us up on the difficulties of building and powering replacement hearts for humans.