Re: Envirotex Lite coating tips

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

Terry, all -

I have used Envirotex-Lite for coating secondaries since 2000, and 
have developed a process that works very well for me. I posted this 
procedure once several years ago, but I couldn't find it in the TCML 
archives, so here it is again:

The epoxy material I use  is "Envirotex-Lite", and it's advertised as 
a "pour-on" coating. The manufacturer is Environmental Technology, 
Inc, and their website is www.eti-usa.com.



There are a large number of consumer and industrial epoxy's that are 
suitable for coating secondaries, but this particular one is carried 
locally (So California area) by the Ace Hardware chain at a 
reasonable price. There are several different "kit" sizes; the quart 
kit contains enough material for at least (4 ) 6" X 30" secondaries.



(Here is a process for applying epoxy coatings that I have posted 
before, but may be of use again as there seems to be a renewed 
interest in using these coatings for secondaries):



I strongly suggest that anyone who is contemplating coating a 
finished secondary, and can cobble up any type of a motorized 
"rotisserie" device to keep the thing turning at slow speed, consider 
using a two-part epoxy instead of any type of solvent-based coating 
(varnish, Glyptal, etc). I recommend a DC gearmotor with an 
adjustable speed control; this allows you to set the optimum surface 
speed regardless of secondary diameter.



Having coated at least a dozen secondaries with epoxy, I can assure 
you that NO solvent-based coating can remotely begin to compare with 
the appearance of a correctly-applied epoxy coating. First of all, a 
single "light" application of epoxy provides a cured coating 
thickness of at least .030"-.050". It would take many, many coats 
(dozens!) of varnish to generate a similar thickness. The total 
"wet-time" of these multiple coats is many times that of the single 
coat of epoxy, greatly increasing the time that the coating is 
susceptible to picking up dust, etc.



Because the epoxy stays "syrupy" until it starts to jell, you can 
flow on a heavy coat very quickly, then allow the coating to 
"self-level" while rotating. This results in a finished secondary 
that appears to have the windings encased in a glass sleeve. Any type 
of solvent-based coating begins to lose solvent, thicken, and 
skin-over the instant that the lid is removed from the can. It's 
impossible to "level" the entire coating on a coil at once when using 
a solvent-based coating.



In the end, the coating ends up being LESS costly then a varnish 
coating!!! I have used a 1 quart kit (2 half-quart bottles) to coat 
(2) 6" X 32" coils, (2) 3.5" X 20" inch coils, (1) 4" X 12" coil, a 
2" X 5" coil, and at least two others. Add the paint thinner, rags, 
quality brushes, etc, etc, required apply multiple coatings of 
varnish, and I guarantee it exceeds the cost of an epoxy coating. I 
think my 1 quart kit cost $17.00 at  Ace Hardware.





Tips:



1. Set up a completely dust free, draft free area to work in. I use a 
bathroom, damp-mop everything, close all windows, etc, etc. A 
carpeted floor is useless; any movement stirs up a cloud of fibers.



2. Very thoroughly wipe down the completed coil with a clean cloth 
moistened with 90% isopropyl alcohol to remove any trace of oil from 
the windings. Even fingerprints may cause "fisheyes" in the completed coating.



3. After all traces of solvent have fully evaporated, I do a very 
careful wipedown with a cabinetmaker's "tack cloth" to pick any 
residual lint or dust.



4. Carefully calculate the volume of material required, based on a 
thickness of .040" or .050". Always err on the high side. I know the 
panic of having to mix up another ounce to finish the last inch of an 
almost perfect secondary. As a portion of the coating will "wick" 
down into the windings, the final coating thickness will be less than 
.040" or .050". DON'T TRY TO APPLY TOO THICK A COATING! Even with the 
spindle turning at a very low speed, circumferential rings may 
develop on the OD of the coil. At first it may seem that there is not 
enough material to completely cover the windings, but continue to 
spread it with the foam brush. Add more coating only if it is 
impossible to get coverage.



5. Mix VERY thoroughly in a meticulously-cleaned, completely dry 
container; glass is preferred, and DON'T use a waxed paper cup.. Use 
a clean piece of wooden dowel to stir. I end up with a froth of 
bubbles, but they seem to all pop during the coating application.



6. Turn on the spindle drive motor & adjust speed to about 5 RPM 
(depending on the diameter of the secondary). LEAVE THE SYSTEM 
RUNNING UNTIL THE COATING IS COMPLETELY CURED! (4-6 HRS).



7. Position a 3-4" wide disposible FOAM paintbrush (NOT a bristle 
brush) against the top of the secondary, and start pouring a very 
thin stream of liquid immediately in front of the brush. The first 
rotation will only spread the liquid slightly, getting better 
coverage with each turn. At this point, the brush is being used as a 
squeegee. Reduce your movements to avoid stirring up dust & lint; 
stand in the same spot without walking around. Have all your tools 
and materials laid out in front of you at arm's reach.



8. Get an initial spiral of liquid applied from end-to-end of the 
coil, then go back and spread it into a uniform coat.8



9. As the coating flows together, reduce pressure on the brush until 
it is barely contacting the surface of the coil.



10. Keep the coil rotating, and inspect for tiny pieces of lint, etc. 
Use a pin to lift them from the surface. Stop the rotation only long 
enough to remove the lint.



11. By this time, 99.99% of the bubbles should have disappeared. Use 
a hot air gun to sweep areas with any remaining bubbles. DO NOT HEAT 
THE COIL!!! Invariably there is air trapped under the windings. 
Applying excessive heat will cause this air to expand and bubble out 
into the coating. The hot air gun temporarily thins the very top 
layer of the coating, and at the same time causes the air in the 
bubbles to expand. Most of the remaining bubbles will pop by 
themselves. Finally, use a pin to pop the last few remaining bubbles, 
if there are any.



(The use of carbon dioxide to cause the bubbles to pop is a myth. 
There is no physical or chemical reason why CO2 should cause the 
bubbles to pop. I tried directing streams of pure CO2 and pure 
nitrogen on early coils I coated, and the gas had no effect on 
bubbles. However, mild heat from a heat gun or hair drier works 
instantly.  The heat causes the viscosity of the surface of the epoxy 
to decrease instantly, and the heat also visibly expands the bubbles. 
Someone has also suggested the use of a propane torch; this is ludicrous.)



12. Inspect the coil for bubbles, pinholes, lint, thin areas, etc. 
When satisfied that everything is perfect, slowly walk out and VERY 
SLOWLY close the door. Make sure no one opens the door until the 
coating is fully cured.