Introduction: Repurposed Cold Frame Lid / Solar Dehydrator
Late summer is the time when I'm (hopefully) overwhelmed with produce from our garden. There's no way we can eat our way through hundreds of tomatoes when they're all at their best, so I like to dry some of the harvest on sunny summer days and pull them out when the snow flies and the garden has vanished for another winter.
I've always used quick'n'dirty set ups for my dryer, like old aluminum storm window screens as drying racks, but this year I was looking for a larger surface and realized the lid of my 4'x4' cold frame would work quite nicely. I also regularly use fabric row cover in my garden as as insect barrier and woodchuck-discourager. Now it has a new use as part of my cold frame lid / dehydrator.
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Not Just a Cold Frame Lid Anymore...
The cold frame I built 25 years ago is still working great (visible in the background of the photo). In my case, the lid of the cold frame uses 1/2" wire mesh hardware cloth attached to the top, which in turn supports a layer of air and water permeable row cover fabric cut to size. During cold spring nights when seedlings are hardening off but still need frost protection, I place a piece of clear plastic over the lid (draped over the sides and with a weighted 'hem' to prevent blowing off in winds) to increase insulation value. When the weather has stabilized the plastic comes off, but the fabric covered lid still gives the plants some amount of safety from a late frost, as well as bug and predator protection. When protection is no longer needed I detach the hinged lid from the back wall of the cold frame and store it.
Step 2: Inverted Lid Draped With Row Cover
This summer I took the lid out of storage to use as my large-surface quickie-dryer. I inverted it, top side facing the ground, essentially turning it into a large tray. I supported it above the ground with a few empty paint cans under each corner then laid a large piece of clean row cover over the frame. The row cover is large enough to act as both top and bottom of a 'sandwich' when I fold it back over itself, with tomatoes (or whatever I'm drying), in between. The row cover effectively keeps bugs and debris out while allowing moisture to escape as the produce dries.
Step 3: Prepare Produce
When preparing tomatoes for drying, I cut a thin slice off the bottom to expose the inner flesh, then make approx. 1/4" slices until I get to the stem end, which I'll discard into the compost bucket. I cut out any funky bits, arrange the pieces on sheets of parchment baking paper (I've tried craft paper as well but the dried tomato slices are harder to remove from it), then give each slice a small pinch of kosher salt.
Step 4: Make a Sandwich and Let the Sun Do It's Thing
I then arrange the sheets of slices in the lid-tray. They're sitting on the bottom of the inside of the lid, so there's about 3.5" of space between them and the top of the lid frame. When the row cover is folded back over the frame, pulled taut and it's corners weighted (I use bricks), the fabric doesn't touch the drying produce but acts as a bug proof, air-permeable cover.
Step 5: Wait a Bit... Then Store and Enjoy Summer in the Off Season.
How long it takes to dry your produce depends on a few variables; what you're drying, amount of available sun, relative humidity and temperature. I live in the northeast U.S. where it can be quite humid, and drying the tomatoes depicted here to my liking took 2.5 hot, sunny days which were very humid. Prepared in the same manner but with sunny dry weather takes 1.5 days. The parchment paper tends to wick some of the moisture away from the slices, increasing drying speed. In really humid weather be on the lookout for mold starting to form if you're drying for longer than a couple days. In that situation I'll bring the nearly-dried tomatoes into the house and finish them up in the oven for a few hours at very low heat (120°-150°f).
After they've dried to my liking I place the slices (most of them... a few are sacrificed to the Tomato Gods who live in my stomach) into ziplock bags for freezer storage, though sometimes I'll store them, immersed in olive oil, in a glass jar.
If you've never tasted your own dried tomatoes, you're missing something great - super-intense, tomato-zilla flavor. Using them on a homemade pizza or combined with basil or parsley pesto (also from the garden, prepared during the summer and frozen in ice cube trays or simply as serving-size blobs on a cookie sheet, then stored in ziplock bags) and served over pasta in the middle of winter is a great way bring some of the garden (and summer) back to life when you need it most.
While I always wait for a forecast of a few days of sunny weather before drying, next year I may mount a couple salvaged lawnmower wheels to one side of the cold frame lid to make it easy to roll under cover if unexpected rain threatens.