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 Post subject: Preval Sprayer Questions
PostPosted: Tue Oct 10, 2017 10:27 am 
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Joined: Tue Feb 08, 2011 6:21 pm
Posts: 240
Location: Charlottesville, VA
Hello Gentlemen,

I'm doing some touch-up work on my Parker and need input from folks that have used the Preval sprayer.

1. Would you recommend that I dilute the gel coat with styrene or will acetone work nearly as well?

2. Should I filter the gel coat (purchased 2 weeks ago) through a paint filter before use, or is this unnecessary?

3. I was going to add wax to the gel coat mix before spraying. Is this OK or would you spray the wax afterwards? If afterwards, how do you spray the wax? I only bought 1 Preval unit.

Thanks all,

Bryce Paschal

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 Post subject: Re: Preval Sprayer Questions
PostPosted: Tue Oct 10, 2017 10:33 pm 
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Location: St Pete/Islamorada
I use them frequently. You should have several on hand so you can do a quick change of the spray canister when it decides to quit and you still have plenty of material in the jar to spray.

Do not use acetone to thin. Use the Styrene. Styrene is made for that purpose but don't use too much. Only enough to get the Preval to work. Too much and the gelcoat will yellow over time after it has cured. Acetone is a good cleaner/solvent that evaporates too quickly which will affect the look and texture of the gelcoat if used as a thinner.

I have never had the need to filter. On that note remove and discard the filter cap on the end of the Preval straw/pick-up.

Add wax ratio 1oz per quart of gelcoat before spraying. The way wax works is that as the gelcoat kicks, the wax moves away from the heat and rises sealing off the gelcoat from the air which is needed to fully cure and become hard. Lay it on about credit card thickness and keep it wet. Too thin and it won't kick. Do not go back and spray over areas that are starting to kick as you don't want to spray over the wax that is coming up.......you'll end up with a mess. Note: always mix wax, MEK, and gelcoat thoroughly in a separate container then pour into the Preval jar to ensure it is mixed completely. Mixing in the jar can miss the the gelcoat on the sides/bottom.

If you are using un-waxed gelcoat, if desired instead of adding wax prior to spraying you can skip that step and spray on a light mist of PVA just as it starts to kick. PVA is a water soluble spray wax and is applied with a clean separate Preval unit. The PVA is green and the light misting is washed off with water and a damp clean towel the next day (or later).

Just a note on the new Parker gelcoats. If you are working with the "new" white "interior" gelcoat, it already has wax added. If the can says "exterior" then no wax has been added. Other than that they are the same. When you are finished with your last coat of gelcoat of "exterior" gelcoat you can add the wax to the last coat for a full cure, or skip and mist with PVA. As long as un-waxed gelcoat is tacky you can add adds coats.

If after allowing for a good complete cure time (day or two) and after washing off the wax, if there is some residual tackiness, use a clean white lint free cloth and dampen with acetone and wipe one time in one direction only. Repeat if necessary. Should result in tack free surface. Always use a sanding block when sanding to keep from burning through.

Remember that working with gelcoat can be more of an art than a science. Cold, heat and humidity are all factors that can affect outcome. And for FWIW acetone and styrene fumes are heavier than air, will sink to the lowest point in the hull and are high flammable.

And yet a final note.......sometimes it's just easier to brush it on with a nice high quality brush and skip the styrene. The gelcoat will tip nicely with a good brush but it will take little more sanding to blend but it does simplifies things bit.

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 Post subject: Re: Preval Sprayer Questions
PostPosted: Wed Oct 11, 2017 7:43 am 
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Location: Pensacola, Fl.
Thin your Gellcoat with Isopropyl Rubbing Alcohol.

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 Post subject: Re: Preval Sprayer Questions
PostPosted: Wed Oct 11, 2017 7:46 pm 
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Joined: Sun May 06, 2007 8:25 pm
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Location: St Pete/Islamorada
warthog5 wrote:
Thin your Gellcoat with Isopropyl Rubbing Alcohol.


Funny thing Wart, Fiberglass Coatings is right here in St Pete and is where I get all my fiberglass related stuff. Every single experienced person who works there says to thin gelcoat with styrene. So now I go to their website and they say DO NOT use styrene because it can yellow. They want you to use Patch Booster now. I was just over there yesterday getting some styrene. lol

https://blog-fgci.com/2016/07/13/tech-b ... g-gelcoat/

Nice tip on the isopropyl, I need to try that on the next project.

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 Post subject: Re: Preval Sprayer Questions
PostPosted: Thu Oct 12, 2017 8:10 am 
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Well I don't do a lot of it and it gets super thin to spray it, which makes it a pain to get coverage, but it works.

They say don't get the stuff that has a Green color to it. I just buy qts of it at Walmart.

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 Post subject: Re: Preval Sprayer Questions
PostPosted: Fri Oct 13, 2017 9:00 am 
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Location: Charlottesville, VA
Jim and Warthog,

I really appreciate the detailed replies.

Might have another go at brush application.


What concentration of isopropyl-OH seems to work for the preval sprayer?

When you mentioned the green stuff, where you talking about the PVA wax or something else?

Thanks again,

Bryce

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 Post subject: Re: Preval Sprayer Questions
PostPosted: Sat Oct 14, 2017 7:20 am 
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Location: Pensacola, Fl.
Quote:
What concentration of isopropyl-OH seems to work for the preval sprayer?

When you mentioned the green stuff, where you talking about the PVA wax or something else?


I just watch it drip off the stick....I know that doesn't help you.....Mixing paint over the years I just know what will go thru.

Experiment.....If it doesn't go thru Clean the sprayer with just Alcohol and add a little more to your mix.

The Green I spoke of to NOT use was a Green colored Isopropyl Rubbing Alcohol.


I just did a job the other day......Brushing will leave streaks......But will get the pinholes filled.

Then you carefully sand it.....With a LOT of care 180gt on the DA making sure to keep it flat, But 180 Wet , Block hand sanding will get it stright and flat.

Then You come back and spray it. That's what I did......Brush, sand and then spray.

Reverse tape on radius edges to make your color breaks blend in.

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