Heat transfer fluid should be changed when contaminated. Dye solution or chemicals, when mixed with heat transfer fluid causes boiling and hot spots within the transfer fluid. This may result in dislodging a dye tank, splashing a dye, or boiling up from the base tank (liner pan).
A crackling or popping sound may be the result of water, chemistry or dye solution being mixed with the heat transfer fluid. For minor spills, idling your system at 130°F. for several hours may evaporate the contaminant sufficiently to eliminate the boiling. Of course, it will not evaporate the pigment from the dye itself, but just the water with which it is mixed. Another sign of heavily contaminated heat transfer fluid is an obnoxious, irritating odor. When in doubt, change the heat transfer fluid.

One way to remove heat transfer fluid is to dip out the fluid as much as possible; another is to use a siphon. Use paper towels to absorb the residue, and wash base with water if needed. This is also a good time to check your heating element.
The silver protective coating which was on your element before will have disappeared after initial use. This was only a protective coating to help prevent damage due to storing prior to installation in your machine. Run your fingers over the heating element. It should be smooth to the touch. If you feel any roughness due to encrusted dye, remove it by gently cleaning with a nylon or plastic cleaner, taking care not to scratch the element.
This inspection is important to you, as such buildups on your element will eventually interfere with proper heating by acting as a barrier, concentrating intense heat within the element, burning it out. It is also a good time to check for bulges on the element which indicate weakness.

In recent advertisements, some manufacturers are claiming that using water as a heat transfer medium is the best way to heat dyes in a tinting system. This is not so, and needs to be addressed so that proper lens coloring can be achieved, and proper health and safety can be maintained in the optical laboratory. To be effective, the heat transfer fluid temperature should be higher than the dye solution inside the dye tank. Tests conducted at BPI have shown that as the dye solution nears boiling, the temperature differential between the heating fluid and the dye tank should be optimized at near 40°F. (To maintain a 205°F dye tank).
This differential requires the heat transfer solution to be maintained at about 245°F. This temperature differential cannot be achieved using water open to atmospheric pressure as a heat transfer medium. The maximum temperature of water at boil is 212°F (100°C), thus making it difficult to achieve the proper dye tank temperature to assure proper color, fade resistance, and color stability.

"Water is an extremely poor choice for
a heat transfer medium for lens tinting"
Dr. William Moore Ph.D. BPI Research Physicist

1. BPI heat transfer fluid Has 7,600 Times Less Evaporation Than Water

2. Water Is 320% Less Effective As A Transfer Medium Than BPI heat transfer fluid

3. Using Water As A Heat Transfer Fluid Can Increase Electricity Costs More Than 500%

Six Disadvantages Of Using Water As A Transfer Medium

1. Requires up to 500% more electricity to color lenses at 205°F.

2. Extra heat and vapor are broadcast throughout the lab, requiring additional air conditioning or ventilation to maintain stable temperature and humidity.

3. Water must be constantly added to the system to maintain the proper level of fluid so that the heating element will not burn out.

4. Dye and other chemicals will oxidize the heating element and fluid container. This causes an acid solution to be formed that causes holes and corrosion in the heating chamber.

5. Water may conduct electricity to the dye solution if the heating element burns out while the tinting system is in use. This could cause a shock if the system is not properly grounded and fused.

6. Since proper temperature is difficult to achieve, colors will fade and are less stable. Especially if the lenses are to be AR coated. The highest dye temperature possible is desirable for tinted AR coated lenses.

Heating water requires large amounts of energy compared to other fluids. It takes about 80 calories to heat a gram of water from room temperature to boiling. Once it is boiling, however, it takes 540 calories for each gram of water you boil away! Extra heat is released into the room and may require additional air conditioning and ventilation to reduce temperature and humidity. A good heat transfer medium expands when heated, becomes less dense, and rises up to heat the dye tanks in the tinting system. (Convection)