Solar dehydrator - Mark 1

I picked a second harvest of blackcurrants the other day. I got three and half pounds and my neighbour got a couple of pounds as well, and there are still more ripening on the bush - it's a good year for blackcurrants. I stewed mine with a little water and strained the juice overnight to make cordial (with sugar added to taste, made about a litre). I then squeezed the bag to get more juice out - the murkier pressing - and made sorbet out of that (dilute and add sugar to taste. Freeze, but take out and stir at intervals. It still needs warming a bit before it's soft enough to serve, but if you don't stir it you just get an ice lolly, which is another option).

Finally, I pressed the remaining sludge through a sieve, leaving behind just the pips and skins, and sludge that I hadn't the energy to push through (this is very hard work). Again adding sugar to taste, this thick sludge can be dried to make fruit leather. As blackcurrants have a very strong flavour, I would have preferred to mix them with something bland like haws, but they're not ripe yet. I think I can live with intensely flavoured fruity snacks. Thick sludge was duly spread out in thin layers on baking sheets.

When I've made fruit leather before, I've dried it in the oven. As we have the novelty of actual sunshine here at the moment - and it's hot! Getting on for 30°C! (OK I know that's pretty cool by American standards, but it's unheard of in Wales) - I thought I'd try the sun dried approach. I started by laying the trays out on the garden table, which is perforated metal, so good for warm air flow around the trays. To increase the chances of actual drying happening, and because I've been thinking about solar dehydrators recently, I decided to construct such a device to help things along.

So... solar dehydrator step 1: Choose something dark coloured and non-insulating to serve as a collector. This is the bit that heats up when it sits in the sun. I picked roof slates as we have lots sitting around. The rigidity is handy, as they need propping up at a suitable angle to face the sun. I used bits of old brick for this, as we also have a lot of these sitting around.

Slates propped up on bits of brick. High tech stuff, this.

The next step is to set up a sheet of glass or plastic over the collector to make a little greenhouse. There should be a gap between the two to allow air to flow from the bottom to the top. I had a broken piece of greenhouse glass to hand, and found a bit of car in the garage (it wasn't attached to a car at the time, I promise!) that looked good for a spacer/ seal for the sides.

Glass resting on piece of rubber. This also keeps the glass off the ground, allowing air to get in at the bottom.

Once I'd set up my collector, I just needed some way of directing the air from the top of it towards the table with the trays of fruit sludge. I also thought that protecting the fruit from flies might be a good idea. I took the fabric part of a tent (yes, that was just lying around, too) and draped it round the table and collector, with the insect net supported by some garden wire (which was tidily put away in the greenhouse). I'm not sure I did a very good job of this.

There are three trays of fruit pulp in there somewhere

The idea was to catch the hot air emerging from the top of the collector and send it in the direction of the table. I did want to take the temperature of various parts of the set-up but the only thermometer I could find (pinched from the central heating system) was very slow to react, and we were going out, so I just left it.

Several hours later...

Tada!

We have actual, dried fruit leather. I didn't really believe it would work. Of course, if I was being scientific about it, I'd have left one tray out in the open as a control condition, to see whether my roof-slate-and-tent setup made any difference at all, but I didn't. I just wanted to give my fruit the best chance of drying, so now I have no idea whether this works as a dehydrator, but I do have a tin full of blackcurrant fruit leather stashed away for the winter.