Rather than a series of standard resistors made to present a 50-ohm load, Joe has mixed up the perfect concoction of household items to achieve a load that presents a perfect 1:1 SWR over a wide range of frequencies.
Those items are a glass jar, water and baking soda.
According to Joe's experiments, straight tap water yielded an SWR of 10:1 at HF frequencies.
One teaspoon of baking soda dissolved into the water brought the SWR down to 1:1 from from 1.8 to 60 MHz. At 144 MHZ the SWR was only 1.5:1.
With the Miracle Whip jar shown, Joe has used the dummy load successfully for 10 years now, at a power level of 300 watts.
A small additional amount of baking soda allows the dummy load to present a 1:1 SWR at frequencies up to 180 MHz.
Further experiments show that a 100 watt rig, at 100% duty cycle requires 50 minutes to boil the water in Joe's DL.
Full details on Joe's chemical dummy load, and the sequence of events leading to its development, are here (15MB zipped file).