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Author Topic:   Thinning Gelcoat with Acetone
Wanchese posted 02-28-2005 04:04 PM ET (US)   Profile for Wanchese   Send Email to Wanchese  
The Spectrum gelcoat instructions used to state that gelcoat could be thinned with acetone; however, now they say that acetone is NOT recommended, and one should use styrene monomer instead.

Has anyone had any problems using acetone? Is this just a marketing thing so you will buy the styrene monomer at $17.78 per quart.

I note that Tom W. Clark used acetone for the major repair in "Repairing Hull Damage the Whaler Way."

Thanks for any and all input.

keltonkrew posted 02-28-2005 07:00 PM ET (US)     Profile for keltonkrew  Send Email to keltonkrew     
I used acetone in my re-do....that's what I was told to use by LBI Fiberglass....although a lot say don't use it...I went with the manufacturer's instructions.
Taylor posted 02-28-2005 07:42 PM ET (US)     Profile for Taylor  Send Email to Taylor     
Acetone from Fiberlay is eight bucks a quart, so the difference is not all that much. Yeah, I'm cheap - but when it comes to materials for a job like this, I don't scrimp. The cost savings is in doing the labor yourself.

If the directions had said 'styrene' that's what we would have used. When I exchanged email with Spectrum Customer Support last year they said that gelcoat formulations had changed since I did my repair and thus their instructions had changed.

There is some discussion of this in the follow up thread to the repair article:

Tonym posted 02-28-2005 09:09 PM ET (US)     Profile for Tonym  Send Email to Tonym     
Some people also recomend a good laquer thinner to cut gel coat. Tonym
bdreaper123 posted 02-28-2005 10:01 PM ET (US)     Profile for bdreaper123  Send Email to bdreaper123     
I used Acetone to thin my gel coat. That was what my instructions said to do. I would do what ever the manufacturer recommends.
Martman posted 03-01-2005 08:12 AM ET (US)     Profile for Martman  Send Email to Martman     
How much do you need? I purchased a gallon when spraying one of my 13' last fall. I still have at least 2/3 left. You are welcome to have some. Just email or post here.
Wanchese posted 03-01-2005 11:50 AM ET (US)     Profile for Wanchese  Send Email to Wanchese     
Hey Marty,

Thanks for the offer. I figure I need about 4 ounces or less.
Hey, didn't I look at one of your boats about this time last year in Wilmington? I bought an old Nauset. I don't have your e-mail. I'll leave mine here. Drop me a line and we'll get together.



John O posted 03-01-2005 09:50 PM ET (US)     Profile for John O    
Hello Martman,

I will be in Wilmington in a couple of weeks for a little R&R and could use a small amount of gel coat myself. I would be happy to pay you for it.

Martman posted 03-02-2005 08:14 AM ET (US)     Profile for Martman  Send Email to Martman     
John O,
I have some white (generic) gel coat and a little 1950-1972? color off white spectrum gel coat. Drop me an email on your schedule.
John O posted 03-03-2005 07:11 PM ET (US)     Profile for John O    
OH, I was looking for Desert Tan. thanks anyway. I will be in Wilmington 3/17-3/20
SMLWhaler posted 03-11-2005 02:30 AM ET (US)     Profile for SMLWhaler  Send Email to SMLWhaler     
I used Spectrum product on the inside and outside of my 13 with excellent results. I followed their recommendations and purchased 1 quart of Slo Patch for every quart of gel coat. Worked like a charm. Kicked the way it was suppose to, ended up with a nice job. I would use what the manufacturer dictates. If it costs a little more, so what. You won't have to contemplate a redo because you took the cheap route.

If I remember correctly I used 3 quarts of gel inside and 3 quarts outside. As previously stated you need 1 quart of Slo patch for every quart of gel. Its expensive no doubt. Finished product will be an accurate color match and very durable.

gtcway posted 03-11-2005 05:56 PM ET (US)     Profile for gtcway  Send Email to gtcway     
SMLWhaler, was that 3 quarts total on the inside or 6 when mixed with the slowpatch? I'm thinking about doing my 15' whaler this summer.
SSMarine posted 03-11-2005 09:57 PM ET (US)     Profile for SSMarine  Send Email to SSMarine     
Thinning gel-coat with acetone is not a good practice, overthining will cause problems with curing, also my experience has been that acetone changes base gel-coat colors. My best results have been with Dura-tec High gloss additive, 50/50 with gel-coat, thinned if neccessary with
M.E.K. Solvent and catylized 2% (14 drops per oz.) M.E.K. hardener. The Dura-tec does not require an addition of a surfacing agent (wax) or application of P.V.A. to get a hard, tack free surface. Dura-tec also makes your gel-coat go alot farther as you mix it 50/50. Be advised that Dura-tec, like gel-coat and other surfacing agents have a fairly short shelf life. It seems most gel-coat applicators have a "recipe" that works best for them, for me this works best!!
SSMarine posted 03-12-2005 08:43 AM ET (US)     Profile for SSMarine  Send Email to SSMarine     
P.S. one important note on thinners, (any thinners)
never thin gel-coat more than 20%. Color change and
non-hardening almost certain. Personally don't find it
necessary to thin more than 10% to shoot gel-coat with airbrush or HVLP gun. Improper hardening is usually related
to too much thinner, incorrect hardener ratio, too low of
temperature, or using a laminating gel-coat without wax or a surfaceing agent,or not covering with PVA. Hope this helps!!

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