A look at Building Dehydrators from scratch

When Building a Dehydrator began by purchasing the light polycarbonate trays. I then designed and built the dryer cabinet around them. After considering various materials for constructing the trays from scratch, and after studying the effects of these materials on some foods, I decided the trays were what were needed. The acids in some foods may react unfavorably with certain metals such as aluminum screen. Wood, as used in dowel rod-type trays may absorb food tastes and odors. Fiberglass screen can leave minute fiberglass splinters sticking to the dried food. Galvanized screen is out, due to its zinc-based coating reacting with foods. One material which I have not tried, and which may warrant experimentation, is nylon screening. If stretched tightly on light wooden frames, this material might be durable enough to withstand repeated use. I do not know of any health problems posed by the use of the material on dryer trays. The trays that we used were simply better than any alternative that I could come up with at the time.
Whatever the size or material of your trays, design the cabinet size around them allowing for sufficient room below for the heat element and room to easily fit the trays within. I am providing the measurements below to serve only as a guide for your own construction process, because the type and size of trays that you come up with may vary from that which I devised. Our dryer measures 48″ tall by 14¾” wide by 16″ deep. The trays themselves measure 13¾” square. A slightly different size tray is available from Excalibur Dehydrators, listed at the end of this article.
In the accompanying photographs and drawing you can see some of the construction details of our dryer. I made the base of heavy one-inch particle board because that is what I had. Quarter-inch plywood made up the sides and top of the cabinet. I ripped 1 x 2s for the framing in the cabinet and for the rails which support the drying trays.
Ordinary screen wire covers the six x six-inch fan opening. Holes cut near the top of each side are covered on the inside with strips of screen and allow moisture and air to escape.
If you do not have one, a wide variety of suitable fan and motor assemblies are available from: W.W. Grainger Distribution Group, 1901 Plantside Drive, Louisville, KY 40299. Request one of their catalogs. This is an electrical supply wholesaler. You may have to have a retailer order this unit for you. Order fan-motor assembly #7C7-27. The cost was under $20. Just remember to use a relatively small fan (about four inches in diameter) to move the air rather slowly through the dryer. You want the fan to ventilate the box and move the heated air throughout, but not to cool the food on the trays.



The 600-watt ceramic heat coil [Top] screws into an ordinary porcelain lamp base. [Bottom]
The heat source is a ceramic heat coil screwed into a regular porcelain lamp base. The lamp fixture is secured to the base and either wired directly to a three-prong plug or through a thermostat. The coil was purchased from a local hardware store and is rated at 600 watts. The cost was less than $5. The lamp base cost about a dollar.
Although it isn’t absolutely necessary, I added a thermostat assembly that I had scrounged up. This addition helped to cut down on tending and tray rotation. The thermostat easily handles the appropriate 100°-150°F temperature range. If you purchase a thermostat, specify a fairly narrow temperature spread for the on-off cycle.
Old unmatched hinges for the door and hooks and eyes for the closures were scrounged from the workshop.

You can easily build your own simple dehydrator from household items and have your favorite dehydrated foods drying in no time. For those of you with a little more ambition and skill, there are larger, more efficient dehydrators that can be built.  For the purpose of this article we will discuss the basic needs a dehydrator requires and we will explain how to build a simple dehydrator for using household items.
The Required Basics
Just like people need food, shelter, and love; your dehydrator has many of the same needs.
Love. Your dehydrator needs some “love” - in the form of heat!  Heat lamps do a great job. You can also use electrical heat coils, an old crock pot base or anything that can put off heat for an extended period of time.
Shelter. Next, you will need somewhere to foster that love. You will need some sort of shelter: a box, an old cooler, an old refrigerator or a wooden box of your own creation. Place your heat source at the bottom with vents near the top of the dehydrator so the heat can rise through the bottom and out the top.
Note:  You don’t want to use any insulation that will trap moisture inside and grow mold.  Installing a fan will increase the rate of the dehydrating process - a fan from your old computer will work great.
Racks. Once you have your dehydrator built you will need some racks. Make sure your racks are removable so that they can be cleaned after use. Preferably, you want your racks to be able to breathe so the air can pass freely through your food - something like a cookie sheet won’t work as well. A wooden frame with wire mesh stapled to the bottom makes a great rack.
Note: Place old window screens on top of the wire mesh for even easier cleaning and to prevent the metal from burning your food.
Food. Once you have your dehydrator built, the only thing left is to give it some food. Your new dehydrator will love some bananas, apples, apricots, meat, or anything else you may want in your food storage.
The temperature of your dehydrator is very important in the dehydrating process. You want your temperature high enough to draw the moisture out from the food but not hot enough that it will cook your food and kill nutrients in the process. Each food you dehydrate will have a different optimal dehydration temperature. As you do your research you will find everyone has a slight difference in opinion for optimal dehydration temperatures. The following list is an overall average ballpark range to shoot for:

Dehydrator Temperatures
Fruit & Vegetables	130°-140° F
Meats	145° F or higher
Herbs	95°-110° F

 
These low temperature ranges are what makes using a conventional oven to dehydrate your food difficult - most ovens do not operate below 200 degrees.
Also keep in mind, the ventilation of your dehydrator will affect the amount of moisture trapped inside, which will in turn affect the efficiency of your food dryer. If there is a lot of moisture inside the dehydrator it will take longer to dry your food.
Building a Simple Dehydrator Using Household Items
Yes, it is true; you can build a dehydrator using household items.This is no Snackmaster Express by any means, but if you have the time and patience this dehydrator will get the job done. It only took me about 20 minutes to have this dehydrator fully operational.
Items you will need:
- Large, closeable box
- One of the Following: Light socket, lamp assembly, extension light, heat lamp, or some kind of safe heat source.
- Aluminum foil
- Wooden slats or dowels
- Racks (cookie cooling racks work great)
- Tape

Step 1 Select a large box (preferably one that can stand up on end for easy access) and line the inside with aluminum foil using tape. I used a 10” x 14” x 14” box.
Step 2 Cut a hole in the bottom side of the box to insert and mount your heat source (try and keep the hole as small and insulated as possible; if you are using an extension light you can just have the cord come out the bottom of the door crack.)  I used a 75 watt bulb in our extension light.
Note: Make certain there are no exposed wires in contact with the aluminum foil—moisture may also accumulate inside.
Step 3 Cut holes in the sides of the box to slide your wooden slats or dowels through to place your racks on.  I used ½-inch PVC pipe.
Step 4 Make vent holes at the top to allow the moisture to escape. I’ve found that having more small holes work better than fewer large holes. I made seven 1/4-inch holes at the top and had some bad condensation accumulation where I did not have holes. You might consider placing four smaller holes along each top edge and additional smaller holes spread throughout the top.
Step 5 Prepare your favorite fruit and place them on the racks.
Note: Do not leave your dehydrator unattended.

Step 6 Close your box and let the food dehyrate!