: Just want to say that just because I am serious about getting an answer to
: this (and have never liked easy answers,ones that are too "easy"
: for their own good anyway) does not mean I am trying to make Dr. Rot or
: anyone look bad. Don and Paul "get" where I am comming from, it
: is only to understand what is happening and not wanting to just take the
: first thing any "expert" may say as gospel if I have a question
: or something doesn't add up. It isn't personal... It more important than
: that it for the BOAT !!! I want to do the CPES but I AM NOT LOOKING TO BUY
: SOME NEW TROUBLE with CPES (or anyone on this board). That's all.

: Paul I notice we have one of the very same concerns although I did NOT post
: this part in my earlier messages. But I did tell Dr. Rot: My hull and deck
: have already been sealed and glassed with "Clear Coat" and fill
: coats of regular epoxy over that. So the CPES will seal the hull and epoxy
: over that will seal in the CPES, just like you wrote this is a cause of
: concern and that is the situation I am talking about. I too would be much
: less concerned if the "other side" were not already sealed.

: Like you said: "Then again, it might not matter too much. You'll be
: applying the cpes and the finish coat on one side of the wood at a time.
: Even if you only wait a couple of hours before putting on your final coat
: of epoxy, the back of the wood is still open enough for those solvents to
: evaporate through that side when the front is
: completely sealed.

: What you wrote without even know that that was my situation was right on!:
: "What I don't like is the possibility that some solvents would be
: trapped in the wood and CPES when you are applying the "final"
: coats of epoxy resin.

: "Polyester resins are thined with solvents which evaporate as the resin
: cures. The evaporating solvents create their own paths out of the resin,
: with the bubbles of gaseous solvents forming microscopic tubes or
: "wormholes" through the resin. After the solvents are long gone
: those microscopic holes remain.
: While they are far too small for water molecules to pass through, they can
: act a bit like Gore-Tex (R) and let the smaller molecules of watervapor
: through. It is a very slow process, but moisture that gets under the resin
: can eventually feed mold or rot spores, With drops in temperature it can
: condense back to liquid water, and if the boat is later left in the sun
: that moisture can turn to steam, which, when trapped under the resin
: causes it to delaminate. The saturation of the wood with epoxy or CPES is
: going to deter rot, and probably not allow a lot of moisture in through
: the solvent holes -- if indeed any gets in at all. Ideally the solvent
: will be totally evaporated before the resin gels, allowing the weight of
: the resin to sag a microscopic fraction of an inch, and pinch closed any
: tubes or "worm holes" that may have been formed."

: Like I said all you wrote was right on, BUT without more understanding (like
: these questions) I have already realized that I am stuck with only the
: uninformed choice of what you also said: "You either wait two days
: before coating the stuff, or you wait 2 hours." This is ok if there
: can be no better knowledge. I would just let the whole CPES seal coat
: evaporate and set up for days, but Dr. Rot says his chemists say the bond
: is much better if the next coat is applied while the seal coat is
: "tacky". Anyway to those who think this is a fair question to
: look for an answer here on this board of boat builders, I'd really like to
: hear the why's or way's of thinking about this. If some think what's the
: big deal, or just ask HIM about it, I only wonder if that couldn't be just
: as true of 90% of the questions posted and asked on this board. I mean how
: many times is "How long before my epoxy gets a blush and I have to
: sand before recoat asked here?" Can't System 3 or MAS answer that
: (They DO right in the book they GIVE you when you buy the stuff), but
: questions like that get posted here day after day, so can't see why
: "Go ask somewhere else" applies to this question. I know I can
: ask Dr. Rot, he seems like a great guy, so that is no problem. BUT I have
: found this board powerful for how much people KNOW and CARE. So I am
: CHOOSING to try to educucate myself before I just go back again for the
: third time (with the same questions) but not one bit more to knowledge to
: help me find out all the facts from him. Anyway I think it is a fair
: question for this board and I have already learned from Paul's points that
: the concern I have of sealing over CPES too soon is real. Thanks to all
: for their time, experience and input. As a novice I try to do the same if
: I think my "knowledge" will do no harm, but if I don't have a
: good idea of the issues involved in a question I don't just pull something
: out of the air, or say why not ask somewhere else.

: Joe

Joe,

I understand your concerns.

The solvents used in CPES (xylene, tolulene, alcohols -- plus 11 others) are highly volatile. On good wood they gas-off quickly, in as little as an hour at 60+ degree temps with good air movement. We and many, many others have put down epoxy resins on top of CPES that has vented off the solvents and reached the "tacky" phase -- when we are in a hurry. Generally, though, if we are applying another epoxy we will wait until the CPES has reached the "non-tacky" phase. The resin that forms the base of the CPES formula does not blush so a wipe-down is not required. If several coats of CPES are applied and the surface cures with a gloss, then we suggest "scuffing" the surface with very light sandpaper or one of the 3M scuffing pads. Most epoxy manufacturers/distributors recommend the same.

Hope this helps clear things a bit.

Jim
THE ROT DOCTOR
http://www.rotdoctor.com
Phone: 206 364 2155
Fax: 206 364 4744