Interlux’s web site has some great information on this process.
http://www.yachtpaint.com/usa/default.asp
The reference guide;
http://www.yachtpaint.com/USA/hotlinks/fiberglass_paintguide.pdf

The number of coats isn’t as important, a thickness of 10 mils is. Thin nap
means more coats, but any painter will tell you many thin coats is better
than a few thick. No need to tip. The product come in white as well as
gray. Alternate colors on coats is a cool trick to track your progress.

The first coat of barrier coat will show you all the spots you missed on the
clean up. Sand the spots, fair and sand, then move on with the barrier
coat. I think you have up to two weeks between coats of barrier coat before
you have to sand to get a good bond. The sooner the better.

The first coat of bottom paint should go on when you press your thumb to the
barrier coat and it leaves a print but doesn’t stick to your thumb (still
tacky).

Prep is key for a successful job.

Chuck.

On Fri, May 7, 2010 at 8:38 AM, wrote:

I’ve hired a contractor to soda-blast the bottom of my boat and I’m
planning to put on a barrier-coat this summer. I don’t have many blisters,
but I have some spider-web cracks below the water line in the gelcoat on one
side of the boat. I’m currently planning to put on 4 coats of interlux
interprotect barrier coat. I’d appreciate comments from those who have been
down this path.

What I’ve learned so far is that I should plan to put these costs on
successively, one or two coats each day as time permits so that I can avoid
sanding between coats. I should also get the first coat of bottom paint on
before the last coat of barrier coat hardens.

I plan to roll the stuff on with a short-nap roller. I don’t know if
tipping is advised. Painting will be done when the weather forecast is clear
and temperatures will be in the 70’s .. 80’s F.

Rich
BlackSheep #47

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Hi Rich,

Your plan is perfect – for the cracks in the gel coat below the water line,
use an old style can opener (beer can opener) and trace all the cracks. Make
sure you get to the bottom of the crack or to the underlying fiberglass.
Don’t worry about going through the gel coat. Make sure they are clean and
dry.

I usually then make a paste of epoxy and colloid powder (West 404) and use
it like Bondo. Fill the cracks that you’ve opened up and let set – after
it’s totally hard, sand and wipe really well with acetone. You have to get
the wax off or the barrier coat won’t stick. Smoothness isn’t all that
important as the barrier coat does a pretty good job filling small
scratches.

Then do the barrier coat as you’ve described. You’ll have a perfect
bottom.

Bob

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s/v Pelican
Pearson 424 Hull #8
http://thesailinglife.blogspot.com
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Bob,

All very good advice. I would add to do a wipe down first so you don’t
sand any wax into the fiberglass. Always wipe down before sanding.

Pete

On 5/9/2010 7:30 AM, Robert Fine wrote:

Hi Rich,

Your plan is perfect – for the cracks in the gel coat below the water line,
use an old style can opener (beer can opener) and trace all the cracks. Make
sure you get to the bottom of the crack or to the underlying fiberglass.
Don’t worry about going through the gel coat. Make sure they are clean and
dry.

I usually then make a paste of epoxy and colloid powder (West 404) and use
it like Bondo. Fill the cracks that you’ve opened up and let set – after
it’s totally hard, sand and wipe really well with acetone. You have to get
the wax off or the barrier coat won’t stick. Smoothness isn’t all that
important as the barrier coat does a pretty good job filling small
scratches.

Then do the barrier coat as you’ve described. You’ll have a perfect
bottom.

Bob

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Sorry, I wasn’t giving complete step by step instructions. I should have
been clearer. You are absolutely correct – Acetone is cheap and wipe downs
are quick. Use more rather than less.

Bob

On Sun, May 9, 2010 at 9:53 AM, Pete Dubler wrote:

Bob,

All very good advice. I would add to do a wipe down first so you don’t
sand any wax into the fiberglass. Always wipe down before sanding.

Pete

On 5/9/2010 7:30 AM, Robert Fine wrote:

Hi Rich,

Your plan is perfect – for the cracks in the gel coat below the water
line,
use an old style can opener (beer can opener) and trace all the cracks.
Make
sure you get to the bottom of the crack or to the underlying fiberglass.
Don’t worry about going through the gel coat. Make sure they are clean
and
dry.

I usually then make a paste of epoxy and colloid powder (West 404) and use
it like Bondo. Fill the cracks that you’ve opened up and let set – after
it’s totally hard, sand and wipe really well with acetone. You have to
get
the wax off or the barrier coat won’t stick. Smoothness isn’t all that
important as the barrier coat does a pretty good job filling small
scratches.

Then do the barrier coat as you’ve described. You’ll have a perfect
bottom.

Bob

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Pearson 424 Hull #8
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Acetone is cheap, but I find it evaporates very quickly and so it requires using a lot of solvent if the wax build up is significant.  “use more rather than less” is correct because of the fast evaporation. I prefer MEK.
Teflon based waxes are particularly hard to remove, you need a solvent with good cutting power and tenacity, one that does not evaporate so quickly. Even mineral spirits, i.e. paint thinner, can work with stubborn waxes.
Experiment with your particular wax.

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Hi Joe,

I agree MEK is a better solvent. But MEK is also extremely toxic and is
linked to all sorts of unpleasant cancers (as opposed to the fun ones). If
you use MEK, make sure you’re using chemical resistant gloves and real
breathing protection that include VOC filters (activated charcoal). MEK is
nothing to fool with. It is readily absorbed through the skin.

The fast evaporation for me is a good thing as the surface is ready to work
sooner. Also, rather than having two solvents (one for thinning epoxy and
MEK), I just use the one.

Everyone makes their own decisions about what to use; both solvents will do
the job. I’ve found that using mineral spirits still requires a quick wipe
with acetone afterwards.

Bob

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s/v Pelican
Pearson 424 Hull #8
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I agree with everything you said..it depends on the tenacity of the wax…always work with good ventlation and gloves, especially with acetone as it enters the pores of you skin very easily.  Acetone is also a suspect carcinogen..but, if you smoke, that makes little additional risk.
Because you are outside and it’s usually breezy and warm, it should not be a health risk.
I’m not saying that acetone is not good, just that you may need to use much more than the low cost justifies, compared to MEK and other less volitile solvents such as turpentine or mixed aliphatics…. and though an acetone wipe is recommended if you use such higher boiling point solvents, it’s a very fast wipe using little acetone.

Most importantly, have fun doing it!  Drink plenty of fluids!

Joe,

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Bob,

I think you may have MEK confused with Methylene Chloride
(dichloromethane). MEK is considered to be a very safe solvent and
safer than acetone as it is absorbed much slower through the skin.
There was a very long study of workers in a “dewaxing plant” who used
MEK and there was no increase in incidence of cancer. Methylene
Chloride on the other hand is very dangerous. Inhaled or ingested, it
can attach to hemoglobin when oxygen is supposed to attach, thus tying
up the hemoglobin. I believe this is the same mechanism that carbon
monoxide poisoning but it is more tenacious than CO. People have used
methylene chloride paint strippers during the day and died the same
night from heart attacks due to the lack of O2 in their blood.

Here are some links to more info:
http://www.epa.gov/ttn/atw/hlthef/methylen.html
http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/mek/health_mek.html#_1_6
(this one discussed the “dewaxing plant” study)
http://des.nh.gov/organization/commissioner/pip/factsheets/ard/documents/ard-ehp-33.pdf

Pete

On 5/9/2010 10:09 AM, Robert Fine wrote:

Hi Joe,

I agree MEK is a better solvent. But MEK is also extremely toxic and is
linked to all sorts of unpleasant cancers (as opposed to the fun ones). If
you use MEK, make sure you’re using chemical resistant gloves and real
breathing protection that include VOC filters (activated charcoal). MEK is
nothing to fool with. It is readily absorbed through the skin.

The fast evaporation for me is a good thing as the surface is ready to work
sooner. Also, rather than having two solvents (one for thinning epoxy and
MEK), I just use the one.

Everyone makes their own decisions about what to use; both solvents will do
the job. I’ve found that using mineral spirits still requires a quick wipe
with acetone afterwards.

Bob

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Hi Guys,

Here’s my two cents worth. When I did the bottom of Xanadu, right after I
had her trucked up to Toronto, the yard foreman at a company called Bristol
Marine where I was doing the work said not to use any chemicals after the
bottom has been sanded off. Just use plain fresh hose water and a scrub
brush. No matter what cleaner or solvent you may use, there will always be
some trace of it left behind that will effect the bonding to the hull. Made
sense to me, so that’s the way I proceeded before applying the
Inter-protect.

Jack
Xanadu IV

On Sun, May 9, 2010 at 9:34 PM, Rich Carter wrote:

HI Rich,

If you use any epoxy or polyester to make repairs to the bottom then you
need to dewax it – (remove the blush). Otherwise, Jack is correct – sanding
and a good washdown will do the job.

Bob

On Mon, May 10, 2010 at 6:58 AM, Jack P Clarke wrote:

Hi Guys,

Here’s my two cents worth. When I did the bottom of Xanadu, right after I
had her trucked up to Toronto, the yard foreman at a company called Bristol
Marine where I was doing the work said not to use any chemicals after the
bottom has been sanded off. Just use plain fresh hose water and a scrub
brush. No matter what cleaner or solvent you may use, there will always be
some trace of it left behind that will effect the bonding to the hull.
Made
sense to me, so that’s the way I proceeded before applying the
Inter-protect.

Jack
Xanadu IV

On Sun, May 9, 2010 at 9:34 PM, Rich Carter wrote:

Wax, what wax? There can’t possibly be wax on the bottom of the boat

after

32 years. Maybe if it were new… Am I missing something here?

I hate working with Acetone. I think it pretty toxic. If I can avoid

the

Well, I’ve been dealing with solvents all my life and have never had any
issue like that – I don’t know if it’s just differences between people (some
people have greater sensitivites to hydrocarbons then others). I’ve used
acetone, trichloroethylene (I think) and others but never MEK. On the other
hand, at the time I was using ethanol regularly in vast quantities that
probably kept my system flushed. At least that’s my theory…

Bob

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s/v Pelican
Pearson 424 Hull #8
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When I get epoxy on my hands (like just now), I clean them off with white
vinegar rather than acetone. Actually, a 50/50 mix of vinegar & water, which
I keep in a spray bottle in the galley for spraying (then water-rinsing)
produce I bring aboard. Vinegar kills most bacteria on the produce, and it
cuts epoxy amazingly well. Leaves your hands smelling like a fresh salad !
(Just kidding.) Seriously, though, it’s got to be a lot healthier on your
skin than acetone. I wonder how it would do as a wash-down solvent. I have
no idea whether it cuts wax, but it wouldn’t surprise me.

I know, I know, you’re supposed to wear protective gloves when using epoxy.
I don’t. My bad.

Tor
~~~~~~~~~~~~~~~~~~~~~~~
Silver Heels, P-424 #17
http://www.silverheels.us
~~~~~~~~~~~~~~~~~~

Interesting thread as it went from bottom coat to the inability to urinate.

Rinse it down with water to remove any dust before applying the first
barrier coat.

A cleaning solvent wouldn’t hurt but isn’t needed.

Chuck

On Sun, May 9, 2010 at 9:34 PM, Rich Carter wrote:

Wax, what wax? There can’t possibly be wax on the bottom of the boat after
32 years. Maybe if it were new… Am I missing something here?

I hate working with Acetone. I think it pretty toxic. If I can avoid the
stuff I’ll feel more secure.

What do you think guys, can I skip the acetone wipe-down?

Rich

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OK..my last post on this topic.

If there is no wax….then of course no solvent is needed.

Sand, wash, and if there is a lot of dust in the air which may adhere to the wet surface as it dries. You can use a tack cloth and a fast wipe..much simpler and cheaper than a lot of solvent. A little dust won’t bother a barrier coat.

But wax can affect adhesion, so hence the concern. I have trouble imagining where wax would come from, unless instead of a barrier coat someone just used wax. I’ve seen that done on fresh water lakes.

Joe,

PS..difficulty to urinate is usually due to a swollen prostate. Not acetone which is NOT highly toxic, and occurs naturally in the body as a product of metabolism of polyketenes.

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we just barrier coated Jubilee this spring. we also had her soda-blasted first. 4 coats interluxe. alternated gray/white (a very good idea). then three coats bottom paint (one red, then 2 black). Interluxe went on really well. timing was important.