A rafting guide friend recently taught me a new minimal water dish washing technique.
1. Scrape all the food into the garbage
2. Rinse the plate with plain water from an aerosol sprayer (in stream)
3. Spray with a weak soapy water solution from another sprayer
4. Scrub with reusable dish cloth
5. Spray with plain water until no soap remains
6. (and this is the key) Spray with restaurant-grade sanitizer, such as Star-San (available at homebrew stores)
7. Air dry (I put a dish towel over the dish rack to keep leaves etc. off.
I recently used this technique for my 20 day teardrop trip through British Columbia and was pleased with 1) the reduced amount of water consumed, 2) the reduced amount of work, no heating water, and 3) the cleanliness of the dishes. No greasy film from the rinse water.
I got through 20 days on the road with only 2-1/2 gallons of wash water.
The sanitizer is the key!
<Chas>
