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Re: [TCML] I think I ruined my 6" secondary.
David -
I think there may be some misunderstandings in this thread.
If Scot's Behr 50 coated coil showed "seperation" between the windings and the Behr 50 epoxy coating after being subjected to an "impact", what occurred was a bond failure between the secondary winding and the coating, and probably had nothing to do with the epoxy "becoming brittle". If the epoxy coating was brittle, it would have cracked, chipped or shattered (spider-webbed) at the point of impact. This type of bond failure can occur if the secondary windings were not carefully cleaned with a solvent (like isopropyl alcohol) immediately prior to applying the epoxy coating. After winding, a secondary is likely to be covered in oily fingerprints (invisible, but definitely will prevent good long-term coating adhesion).
The 2-part epoxy coating actually named "pour-on" is "EnviroTex Lite pour-on HIGH GLOSS FINISH" (as written on the package). This is sold by Environmental Technology, Inc in Field's Landing, CA. (See: http://www.eti-usa.com/consum/envtex/envlite.htm). In Southern California, I have purchased this material at Ace Hardware stores.
I've used this material over the last ten years to coat over a dozen secondaries (#22 AWG through #34 AWG) and it has performed spectacularly. One coat provides a very thick (at least .050"), slightly flexible, glass-clear coating. I've never had any problems with delamination, cracking, crazing, discoloration, or secondary damage from "racing arcs" or self-strikes. When done correctly, this coating yields a thick, transparent, mirror finish that looks like the windings are encased in a heavy glass sleeve. I've dropped secondaries, accidentally knocked them against all sorts of other objects, scraped them against sharp edges, etc, etc and never sustained any significant damage.
The EnviroTex resin has a viscosity similar to heavy syrup, and a motorized fixture is required to keep the secondary slowly rotating for several hours while the epoxy cures. Pot life is at least 1/2 hour at 70 degrees F, and gel time is about 2-3 hours with full cure in about 12 hours.
At one point I also tried the Behr-50 epoxy, but I didn't obtain as good a finish as I got with the EnviroTex material.
As Scot noted, epoxys are very good insulators and make good electrets. After running a Tesla coil with an epoxy-coated secondary, disassembling the system always provides some fun when removing the secondary. I've taken some good discharges to the forehead and the navel when lifting a 6" X 32" secondary out of the primary supports. Depending on the ambient humidity, this secondary is usually good for at least 2-3 good jolts.
Herr Zapp
David Rieben <drieben@xxxxxxxxxxx> wrote:
Hi Scot,
So you're saying that the Behr's 50 will eventually
deteriorate over time? I think that's the first negative
trait that I've heard mentioned about this stuff. Well,
like I said, it takes a bunch thin coats of the Minwax
Marine Spar Varnish to build up a shell of decent
thickness but I agree with Bart Anderson that this is
one of the best commonly availabe products for the
secondary coil coating. My Spar Varnish coatings
have always lasted for years w/out significant dete-
rioration in my unclimate controlled shop. I had
thought that the Behr 50 epoxy would be great but
your comments about its lack of long term durability
have got me questioning its suitability now....
David Rieben
----- Original Message -----
From: "bunnykiller"
To: "Tesla Coil Mailing List"
Sent: Thursday, July 03, 2008 7:05 AM
Subject: Re: [TCML] I think I ruined my 6" secondary.
> Hey David..
>
> The pour on stuff I used was Behr 50, a 2 component material. It was
> very nice to use, thick like an epoxy ( I believe it was an epoxy) once
> dried it was somewhat resiliant, but after a few years it becomes very
> brittle and when you bump the coil, the wires seperate from the coating,
> leaving large "air gaps" between the wire and coating. I do have to
> admit tho, the exterior finish has held up to years of abuse with
> minimal scuffing ( still shiney) and one more thing, the Behr 50 is
> quite prone to the effects of holding a charge on the coil ( very strong
> zapping capacity :) on my 12"X5' secondary it was like being hit by a
> Taser, couldnt move my leg properly for a couple of minutes after the
> main shock).
>
> Scot D
>
>
> David Rieben wrote:
>
>> Hi Phil,
>>
>> Can you tell us what the name of this stuff is? I have heard
>> of Berh's "pour-on" but have never been able to find a pro-
>> duct by that particular name in my local building supply stores.
>> (Plenty of Berh's paint products, but no Pour-On).
>> I have been using the Minwax Marine Spar Varnish on my
>> coils for the last several years now with good success but
>> of course it has to be applied via multiple thin coats to get
>> a reasonably thick coating.
>
> snipperz
>
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