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Author Topic:   Gelcoat Repairs with Spectrum Color Resin
jimh posted 11-06-2000 07:41 PM ET (US)   Profile for jimh   Send Email to jimh  
I go some of the "OEM" color gelcoat from Spectrum Color. The stuff is so thick I cannot imagine how it can be sprayed.
Please tell me:

--how does this thin with Acetone?

--how does this thin with Styrene?

--how thin does it need to be to spray with the little Preval sprayer gizmo?


Dan posted 11-06-2000 07:57 PM ET (US)     Profile for Dan  Send Email to Dan     
Spectrum has a web site, I forget the url, the site has instructions to do what you want. The intructions are in Acrobat PDF files and are very good. Good luck.
Barry posted 11-06-2000 09:33 PM ET (US)     Profile for Barry  Send Email to Barry
kingfish posted 11-06-2000 09:59 PM ET (US)     Profile for kingfish  Send Email to kingfish     
I don't believe the Spectrum patch paste *can* be thinned enough to spray, with a Preval sprayer or with any other kind. I don't think it was designed to be used that way. I believe in general you are limited to introducing a maximum of 20% thinning agent by volume, and while I haven't tried it with the patch paste, I have with Spectrum gelcoat (bought by the quart, *not* paste)and adding 20% acetone to that thins it enough to use in a preval sprayer. I have to think adding 20% thinner to the paste would only thin it to the consistency of malted milk.

Thinning the regular gelcoat is done by measurement *before* the MEKP hardener is added.

Dan and Barry are spot on - the Spectrum directions on their website are very clear and complete.


kingfish posted 11-06-2000 10:21 PM ET (US)     Profile for kingfish  Send Email to kingfish     
Some additional thoughts-

-I'm going to experiment some more with the thinned Spectrum gelcoat and the Preval sprayer, and I will report what I find, but at this juncture I have not had a completely successful experience with that combination. The Preval sprayer has a pretty small orifice and I wound up thinning pretty close to the maximum 20%; the result was that I had a hard time getting much thickness built up and what I did have was so thoroughly orange-peeled that when I sanded it flat, most of it wasn't there any more. I'll be trying thinning it less, and spraying closer, so the gelcoat isn't dry when it arrives. We'll see.

-The Preval sprayer works outstandingly well for spraying PVA curing sealer. (It's really a clever little device - just may be more effective with paint than gelcoat.)


lhg posted 11-06-2000 10:52 PM ET (US)     Profile for lhg    
Here's a quotation from the article I was going to send you guys regarding spraying gelcoat:

"Even better (than the Preval unit) are miniture spray outfits called "air brushes."
Sold in hobby shops and art supply stores, inexpensive models are also powered by a disposable can of aerosol type propellant or compressed air. These are usually more versatile than the Preval unit because they come with an adjustable nozzle that enables you to regulate the spray pattern.

When gelcoat is to be sprayed it must be thinned with acetone to about the consistency of skimmed milk. Add the thinner a little at a time, then stir to check consistency. You can always add more if it is too thick, but you have to start over again if it is too thin. If the gelcoat is too thin it will run and drip and may not cover as well as it should. If it's too thick, it will not come out of the sprayer evenly.

Do your thinning before you add the catalyzer. Experiment on scrap pieces of cardboard. If the gelcoat spits or spatters, it's too thick, or the nozzle may need adjusting. When you finally get a nice spray pattern, add the catalyst and go to work. Several thin coats are better than one thick coat, because the material is less likely to run and will come out smoother.

BW27 posted 11-07-2000 12:07 AM ET (US)     Profile for BW27  Send Email to BW27     
I recently used the Spectrum gelcoat. I used both a Preval sprayer and a Royal sprayer. I much preferred the Royal brand disposable as it had much more power and gave a more even coat.

I thinned 15%. The color match was great.

The Royal came from Fisheries Supply in Seattle and cost about $8

sport15er posted 11-07-2000 02:14 PM ET (US)     Profile for sport15er  Send Email to sport15er     
jimh, I use the Spectrum also, but have never sprayed it, you may want to chk out this site when you get a chance:
I haven't personally bought from them, but they do sell a sprayable gelcoat (Boston Whaler colors available), and there's a little mpg movie on how the spray system works that you may be interested in seeing.
Perhaps when I get a project boat to play with, I'll try it out; on my one & only I'm sticking with Spectrum for the time being......
jimh posted 11-08-2000 12:55 AM ET (US)     Profile for jimh  Send Email to jimh     
Thanks for the replies.

I have the paste stuff--it is about the consistency of tooth paste.

I also have some generic white gelcoat, and it too is pretty thick. It would need a lot of thinning to be able to be sprayed (unless you had a rather powerful spray gun).

Also, I too ended up using the PREVAL sprayer to apply the PVA topcoat, instead of the gelcoat. I brushed the gelcoat on.

I'll check the Spectrum website for more info.


wawashkeshshinini posted 02-02-2006 03:38 PM ET (US)     Profile for wawashkeshshinini  Send Email to wawashkeshshinini     
In regards to the technique in spraying gel coat. Please try using one of the ESTES model car spray kits. You can find them at any Walmart. They come in two differant kit forms and are very cost effective. You'll get a variety of paint with either kit, but consider it a free-be. The cost of either kit is equal to the cost of one preval kit. You can sray upside down and at differant angels with the kit that has the mini gun. The prevals are always a hassel and make more of a mess than anything else, and you always seam to get a massive amount of orange peel. On the ESTES: One has a top that snaps onto the aresol can and the other has a 6 ft. long tube that screws on top of the can with a mini touch-up spray gun attached at the other end. This one works best. I have used it in every gel coat job; They both work very well and I have never experienced orange peel with the use of either kit. Give it a try.
acassidy posted 02-03-2006 10:46 PM ET (US)     Profile for acassidy  Send Email to acassidy     
Spectrum has 2 different types of gelcoat and I have used both.

The patch kit (probably what you ordered) is thickened almost like the consistency of marine tex made to be puttied on the repair with putty knife. You must use this product as is and do not thin it.

The quart gelcoat is un-thickened pure gelcoat. This has the consistency of latex paint and you must add the curing additive that is included (wax) and any thinning and thickening agent you would like. I have rolled on this product with excellent results. I have also thickened this with Cabosil and did large repairs on the keel.

Hope this helps

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