I have never tried the solar method but would like to and have a couple of questions that I haven't seen addressed.

1.) For you guys in the humid climates, doesn't the dirt collect moisture underneath the plastic sheeting even if it is bone dry before starting (if there even is such a thing in humid climates)?

2.) What is the minimum temperature that the solar method works? I could wait until the humidity goes down in the fall but then I'm afraid I won't have enough heat.

3.) Black or clear plastic best?

1) dirt goes in top of plastic sheet
2) I like it to be 85°F, I do it on the leeward sunny side of my barn and works even if humid out but not as fast as when humidity is low (dewpoint under 60°F)
3) black plastic

1- Humidity? Fortunately it is very dry here. I cannot help on this one.

2- 80 plus temp, clear sunny day, not to much wind, angle of the sun hitting the waxed dirt are important in melting the wax now that the days are getting shorter.

3- I prefer Clear plastic and keep it from touching the dirt. If you use Black plastic then set it touching the dirt. I only used Black plastic Once!
Clear plastic has been a winner for me. Hope this helps!

I did mine here in humid conditions. Mixed dirt with wax in 3:1 ratio and spread out in a dark blue tarp. 75-80 deg day and it was well melted in about 3 hours. I stirred it a few times with a rake during that timeframe. My first time doing it that way so we will see how it works this season.

This is a big deal from my experience. I’m near the 44th parallel and found I have a window of opportunity from about mid-June to 3rd week of July. After that it takes way too long to get my sand/dirt/wax up around 140* and stay there for a short period of time to get a good soak.

I made 50# batches with storm door glass panels over the tubs so I could jack the temp up.

I use the tubs/ storm doors method as well. works great

This is was my method and could be what FHF is also speaking of, or something similar.
https://youtu.be/_qNTGNJGQ7s?si=T55uVTF9gjqU8K15

BTW- I am selling my waxed sand for $1/lb and waxed dirt for $1.50/lb, plus shipping.

I found a 4'x8' glass top for a patio table so made a 4'x8' tray out of 2x4's and plywood. I then painted it flat black and now can do about 15 gallons in just a few hours. Tilt it to max out the exposure to the sun and humility shouldn't be a problem.

I go to Lowe’s or menards and buy their black plastic concrete mixing totes. I dump 4.5 gallons in and add the wax. I’ve done it with an old window on top. But now I just do uncovered in my driveway. I go stir it about every other hour. Once it’s all melted I pull it into the garage and keep mixing for about 15 minutes to prevent clumping. I can post a picture of the tote, but it’s basically like a small otter sled. I use one to drag critters during season as well.

I do 10 gallons of sand at a time. Use a 10 x 12 ( I think it is ) plastic tarp on the ground in front of my South facing barn. Put two five gallon.buckets of sand on it and spread it out thin. If any moisture in it, it will soon be gone. Sprinkle wax on top. Wait until all there is is wet spots where the wax was. Now grab a corner and.pull until all the sand is to one side, then pull it back. Now go the other direction back and forth. Not long and it is all the same color. Shovel back into buckets and take inside to cool. Pour back and forth into other buckets a few.times to prevent clumping.as it cools. Still hard and hot work but gets a lot done fast.

1.) not if it is very dry
2.) 80 minimum here
3.) Black plastic tub with glass over it.