Message-Id: <v01510101ada68154d41c@[199.170.68.46]>
Date: Fri, 26 Apr 1996 08:44:31 -0500
To: baidarka@imagelan.com
From: shaysnet.com!laughing_loon@imagelan.com (Rob Macks)
Subject: Re: Copy of: Pin-holes
>Don, I'm no expert but I am working on coating probelems of my own and
>through testing have learned from my own mistakes and advice from some
>really good people. This information I submit should offer additional clarity
>for Hyplon or other compounds:
>
>
>Many technologies cure progressively and slowly from their surfaces
>inward, like paint. To achieve the build-up of any MEANINGFUL
>THICKNESS, several of these thin layers must be applied, always allowing
>sufficient time between the layers for each to thoroughly cure from
>moisture they take from the air before another thin layer can be applied.
> If a too-thick a coating (too-viscous) should be attempted (been there done
>that), its air-exposed surface would SKIN OVER first, leaving the
>still-wet interior without the air-moisture contact needed for its curing.
>
>As curing slowly progressed from what moisture could penetrate that skin,
>the product of cure, carbon dioxide, would accumulate in small bubbles
>between the membrane and its Nylon substrate, being unable to rise and
>release through the skin. This "GASSING" as it's commonly called, can
>accumulate its small bubbles to cause blisters and even complete
>delamination of the membrane from its substrate. Someone pointed out that
>ambient temperature is important and helps cause an even cure throughout
>any thickness.I believe this to be excellent advice given to perform our
>coating at a lower (or cooler room temp)I have discovered too that it is
>imperative that the substrate be severly penetrated. The base membrane
>mixture must be fluid enough to allow easy spreading, sufficient
> self-leveling to eliminate any marks caused by spreading and the easy
>rise-and-release of any bubbles of whipped in air. To reiterate... Air
>that has been trapped by too viscous a base membrane mixture, or for any
>other reason, may cause a surface blister IF A RISE IN TEMPERATURE causes
>it to expand while the base membrane is still fluid. I have also learned
>that not all solvents used to mitigate the thickness of your coating
>compound are ideal. For instance I attempted using alcolhol as a carrier
>which I soon discovered inhibited the curing process and was a source of
>gassing within the compound. Naturally I desired a more environmentally
>friendly application but NO DICE! Xylene is for me the solvent of
>choice(not because of it's toxic effect on the liver , kidneys and
>brain)USE A GOOD INDUSTRIAL CARTRIDGE MASK by all means while using such
>a powerful carrier to penetrate the nylon substrate for that all
>important initial base coat.
>
>Of course use only what the manufacture recommends. There is old
>technology and there is new
>technology and at present I'm testing the new which looks promising.In
>any event I am working hard to prove to myself new potentials. It sure is
>easier to relate to someone elses concerns when you have experienced
>theirs for
>yourself.
>
>I wonder if George ever produced a coating manual other than his
>commentary in his book "BAIDARKA"? I hope this information is of some
>help to you but I would certainly defer to George's experience.
>
>Regards,
>
>
>Philip Wylie
>"The location of all creativity is in pure awareness...
> The eye refuses to see what the mind does not know!" ( Deepak Chopra )
>
>
> email: pjwylie@freenet.edmonton.ab.ca
"Off gassing" is also a potenual problem in wood strip construction and is
addressed in the epoxy literature. Rising temperature will cause the
trapped gases in the wood, or in your case canvas, to expand creating
bubbles in your coating. Dropping temperature causes the gasses to contract
eliminating the problem.
A high temperature for me in strip building makes my resin thinner
penetrating better, so I heat my shop and boat and then let the temperature
start to drop before I coat any surfaces.
As long as you coat during dropping temperatures "off gassing" should be
no problem.
Rob Macks
Laughing Loon Custom Canoes & Kayaks
http://www.shaysnet.com/~robm/