Gel Coat is tacky.

I have a 15 ft trihull bassboat,its fiberglass,and i just tried my first gel coat application and thought i was finished,but.The gel coat was tacky,after about a week.I used 2 quarts mar pro white gel coat,with a mar pro pigment,and an mkp peroxide.I mixed a quart of gel coat,with 2 oz's of pigment and added 8 cc's of mkp peroxide and mixed very well.90 percent of the quart was rolled on with a faom roller for smooth surfaces,the rest was brushed on in the hard to roll areas.I waited 48 hours before applying the second coat of gel coat which was mixed the exact same and applied the same as the previous steps stated previously.I then waited about 36 hours after that before i checked my work,and the gel coat is still tacky,since then,it has been a week and is still tacky.Does anybody know what i did wrong or didnt do,because im stumped.When gel coat cures is it supposed to be tacky,because i fear if i put on a clear sealer,it would just be mushy and unstable.

Re: Gel Coat is tacky.

Hi Stryker85,

What kind of ambient temps are you working in?

Re: Gel Coat is tacky.

Gelcoat must be protected from the air in order for it to cure. Sounds like you did not use a release agent.For the final coat, a PVA curing agent must be sprayed onto the surface as the gel coat begins to gel. This agent creates a thin film on the surface of gel coat. This film seals off the air and allows the gel coat to cure to a hard finish. The agent can be washed off with soap and water after 24 hours.

Re: Gel Coat is tacky.

Woodonglass said:

Gelcoat must be protected from the air in order for it to cure. Sounds like you did not use a release agent.For the final coat, a PVA curing agent must be sprayed onto the surface as the gel coat begins to gel. This agent creates a thin film on the surface of gel coat. This film seals off the air and allows the gel coat to cure to a hard finish. The agent can be washed off with soap and water after 24 hours.

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Great bit of info there Wood, I did not know this...you see, you do learn something new everyday!!!

Re: Gel Coat is tacky.

A couple of things.

You need to add wax to the final coat, this does the same thing as PVA, only it's easier to do and buy. This about the only way to get a fully cured surface, well there others, but these are lowest in cost, work well and is readily available.

You need to add at least 15cc's of catalyst, and preferably 20 to a quart of gel coat for it to cure correctly.

Re: Gel Coat is tacky.

ok,so do i need to remove the gel coat and start all over again,or can i salvage what is on there?If i want to step up the catalyst to 15-20 cc's and add wax and try this then what type of wax should be added and how much per quart?Is it true that some wax may not come to the surface and could render the gel tacky?

Re: Gel Coat is tacky.

Spray a section with some PVA and give it 24 hours then wash it down and see if it has cured. If so, then do the rest. If not then take it off and re-do it. Don't skimp on the PVA, it takes a bunch. A gallon is less than $20 bucks. The overall cure could still be suspect. So like I said you might want to re-do it.

Re: Gel Coat is tacky.

ondarvr said:

You need to add at least 15cc's of catalyst, and preferably 20 to a quart of gel coat for it to cure correctly.

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You beat me to it; under-catalyzed.. I am afraid that this may be the biggest issue. There are some factors to weigh in on the cure; temp, humidity, etc. Wax or some other additive is needed to give a hard, cured surface (only on the last coat). Without being able to touch it, my gut is saying that you'll need to remove what was laid up. Anything else that you put on top will only bond as good as good as the substrate. You could try and spray some PVA over an area and let it set for a day to see what happens (then wash the PVA off). If the test area doesn't sand well then I am afraid you know what needs to be done. If it hardens up and sands like it should, it will still be under-cured but may be OK for topside areas. If any of this gel is below the waterline you'll want to layup new stuff IMO. Let's see what others say

~BWT

Re: Gel Coat is tacky.

ok,im going to get some more gel coat tomorrow,and ill get the pva and try to cure what i have first,and if it doesnt work,then ill start over,i still have 2 months before the spawn in florida gets going so thanks for the advice,ill reply by tuesday evening and let you guys know whats happening with it just incase i need some more pointers.

Re: Gel Coat is tacky.

Once the original cure cylce has finished using PVA over the surface won't help. If you feel like taking a slight risk, just go over it with a new layer of gel coat with wax. For anything above the water line it should (maybe) be OK.

Re: Gel Coat is tacky.

yeah......ondarvr is correct......

pva wont help now.
pva only works if it is applied minits after the application.

add wax at 3% to the next layer......and catylize a t 2% of the gelcoat.....not gelcoat and wax together.

the reason for the wax or pva is because air inhibits the cure of polyester based resins......so if wax is added to the mix...it will come to the surface of the gellcoat....and make a barrier between the air and the gelcoat.

using pva after you use a non waxed product, is another step in the process. but it is easer to remove during sanding and fairing.

i always use the metric system to mix my stuff.......it is soooo easy.....it is really hard to mess up with cat rates.

Re: Gel Coat is tacky.

yes for this job the project is above the waterline,but ive got this stuff everywhere,i sanded and gelled the whole topside including box lids and trim,the prep job was pretty outstanding,i put in 40 hrs of prep before hand,but i didnt do my homework and now im paying for it slightly.I removed a small portion of the gel and it appears that the first coat cured somewhat,it get harder to clean the gel and its even hard to the touch,so im gonna take a thin layer of it off and see how much it actually cured underneath.
Im buying gel coat that has wax in it this time,from Spectrum Colors in St. Augustine,should i also get the pva for an added protector,and when should i add the pva,imediatly after the last coat?or should i finish an area,spray that area with pva,then move to the next area,kinda like a grid pattern?
So if im opting to buy the gel that has the wax,i shouldnt need to add more wax right?Im doing this job in a barn that has no doors but is dry in side for the most part,and the temp is in the 50's at night and mid to upper 70's during the day.i dont have the luxury of doing this in a controlled enviroment,but,im sure that the pva after the final coat and beefing up the catalyst amount is what i did wrong that can be helped.
Lots of good information guys i really appreciate it.

Re: Gel Coat is tacky.

Do not buy gel coat with wax already added to it, get the wax separately and add it yourself. You could buy some PVA, but the two don't get along all that well when used together, the PVA will bead up on the surface and then run and sag easily when used over waxed gel coat.

Re: Gel Coat is tacky.

ondarvr said:

You could buy some PVA, but the two don't get along all that well when used together, the PVA will bead up on the surface and then run and sag easily when used over waxed gel coat.

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Yes it will bead up and sag, I've done it. Listen to ondarvr and just add wax. I add the wax at 2% and its just fine, but I'm sure 3% as oops! said won't hurt a thing.

With the wax added and properly catalyzed, I was sanding her down the next day with no problems at all.

Woodonglass...they are correct about adding PVA after the cure time...tried that too once and it won't help a bit. Sorta past the point of no return.

Re: Gel Coat is tacky.

ok bud......

we have to go back to some basics here.......you are missing lots of info.....i dont mean to speak for ondarvr....but i know he does not have time to type the whole process out.
ondarvr is a factory rep ....most likely for the gellcoat that you are using. so do what he says.

ok......

1. air inhibits (stops/slows/screws up) the cure of poly based resins.
if you use gellcoat with wax in it.....it will come to the surface in the first few minits of the cure.

2. wax is a release agent......that means poly based resins will not stick to it.....if you shoot gell over a wax cured area....the new layer will not bond.

3. this means that you shoot all in one shot......all of it.....no first or second coat. (do not spray a coat....let cure...then spray a second coat like you do with paint.)
you can walk around the boat a few times....shooting as you go....but you must get back to the starting point before the first layer starts to go...because the wax will start to come to the surface.
if shooting smaller parts/areas....it is done all at once.

4. wax is called airdry. and sold separately....it can be purchased in the product (aka waxed resin or waxed gellcoat. but once the wax is in the product, there is no way to get it out, so you have a product that can only be used as a final layer product). if you purchase un waxed.....and add you own wax. you can use it when ever you want.... and just add the wax in the final layer.

5. gellcoat must not be too thick or too thin when applied.......it must be applied at a final depth of 35 thou. you can get a mill gauge from any paint store.
you can shoot at 50 thou,,,,and sand down (knock off the orange peel) to 35 thou.

6. there are two methods for wax......on the east coast.....the common practice is to shoot un waxed.....then after the shoot....spray with pva.....(this must be done out of a gun, and not a plant mister. the mister will clog instantly and you are hooped.
the pva can be washed off after the cure with soap and water....

the reason for this, is because when you start to sand......sanding with wax, paper loading is an issue till you break thru the wax,,,,then it is not as extreme.
small areas are not as bad.....but large areas like a full hull....it is costly and a real headache.

on the west coast....we shoot wax in.. at 3%....

use one or the other (pva ro wax).....not both.....you are working against your self.

you can shoot the part with unwaxed gell......and on the final walk around, add wax to the gell.... just make sure your coverage is good. or it will be blotchy.

7. when shooting a project........you have to have a plan.....you are shooting really really thick.....so sagging is a real issue. that is why a walk around is common....giving the gellcoat a little time to start to set up before the next layer goes on.....(but nowhere near a cure)

8. cat rates.......1.5-2.5% OF THE GELLCOAT....no more....no less.......a really hot batch is 2.5%.....this gives you very short time in the pressure pot......you have to shoot the whole pot in under 10 minits or the gellcoat will start to go off in the gun, the lines, the pot......and you are hooped.
I shoot at 2%. this gives me 15 minits from mix to empty pot.....

9. mixing. thinning, adding of products to gellcoat.
mixing must be done thoroughly......when you think its mixed ...its not......you can add a pigment to gell coat......mix with a stick for 5 minits......and still see a full strand of pigment come to the surface after 5 minits of vigorous mixing in a small cup or pail.
i use a egg beater on a drill....you want a vortex to srart....and keep that vortex going for a full 3-5 minits depending on the size of the mixing container.

9 a. adding thinners like acetone or patchaid......NO MORE than 10 %...wax is added to a maximum of 5 %....i use 3%
gellcoat is very very thick........the tendency is to add thinner till it shoots nicely like paint.....gellcoat is not paint....adding other chemicals distorts the molecular chain as the gellcoat starts to cure......this will give you a weaker final product, and cracking or crazing will be an issue in a few years.

most gellcoaters don't get to see there work after 5 years....so they don't see what happens to the product over time. they might thin at 30%......the product goes on well, and cures hard....so they think it worked.....but after a few years...it will fail...but they never get to see it as the boat has most likely been sold, or the owner has moved on.
sticking to the manufacturers instructions is the only way to maintain it integrity of the product.

these are some basics......you really need to grasp these concepts.....so your shoot goes well.

i did not get into the gun or pressure pot system at all. but if you pull a search....there are several threads on the subject.

cheers
oops