I saw this elsewhere, and built one of my own. It worked really well on my latest parkerizing project.

Parts list/Bill of Materials (Lowes part numbers):
3" SCH 40 PVC pipe, 10 ft (23834) $10.44
3"x1.5" PVC coupling (23319) $2.97
1.5" SCH 40 PVC pipe 18" (256098) $2.20
1" PVC adapter (the gray piece, from conduit aisle) (115917) $ .89
Water Heater Element, Stainless Steel, 5500W (26367) $16.98

Cut pipe lengths to suit. I cut the 3" to 20" and the 1.5" to 10". 10" will shroud the heater element; it'll be a snug fit but if you don't overpower the heater you will not melt the pipe. I own a variac, but a dimmer switch should work fine based on the original posting about this concept I saw elsewhere. The sheet with the heater element reads "220 Volts" but it works on less just fine. Voltage guidelines below.

Purple primer and PVC cement the pipe & adapter segments together
The water heater element threads match the 1" adapter

I found that 50 VAC brought the 3/4 gallon of water to 83° C in 60 minutes.
and in trials 48.5 VAC took 72 minutes to do the same. 39 VAC took 125 minutes (yes...2 hours) to get to 83 C. 48 to 50 Volt range will push the 83 C solution above 90 C in another 10-15 minutes, so baby sit your parts in the solution and turn off power when thermometer reads say 87.