Gel coat tinting

[SaltytSal]

Just curious if what I did will be acceptable for use.
I began to repair some damage on my boat - which I filled and
restored with Marine Tex. The color of the hull is a sky blue.
I prepared 3-4 ounces of WHITE gel coat. It took nearly an
ounce of Evercoat tinting agent to get the desired color.
I just found out that the ratio is usually 1 ounce of tinting agent
for quart of gel coat. Would I be wasting my time trying to apply
what I prepared?? Would the gelcoat adhere?

Thank you,
Sal Giosa

 

[Woodonglass]

Re: Gel coat tinting

Prolly not. Marine Tex is a Epoxy based Product and Gelcoat is a poly based product. Poly does not adhere well to Epoxy. Having said that if you sand it well with 60 grit and wash it down well with Acetone it MIGHT, emphasis on MIGHT, work. No Guarantees.

 

[SaltytSal]

Re: Gel coat tinting

Yes- but what worries me is the ratio of the tinting agent to the amount of gel coat being used.
Can I use this gel coat?

 

[Woodonglass]

Re: Gel coat tinting

I would PM Ondarvr. He is one of the Forums BEST Gelcoat experts and if anyone can help you with this it would be him.

 

[SaltytSal]

Re: Gel coat tinting

Thanks Woodonglass. Will do.

 

[ondarvr]

Re: Gel coat tinting

That is a very high pigment loading. The problem you run into is the resin used in the pigment is sort of a dead product, it's formulated to last a very long time on the shelf and not get hard, which means the more of it you add to the gel coat base, the slower and poorer the cure will be. Not knowing the exact base or the exact pigment used makes it difficult to say how well it will cure.

Was this a white tint base or neutral? The difference is white tint bases are used for whites and off whites (kinda makes sense), neutral tint bases are used for darker colors that can't have any white in them. Neutrals are sort of a dirty semi clear, grayish, tannish color. Using a neutral base to make a bright white may cause problems.

The other part is like WOG said, it may not stick all that well, paint will stick great though.

 

[SaltytSal]

Re: Gel coat tinting

Hi Ondarvr-

The base tint was white. Perhaps I should scrap it and start off with neutral base??

 

[ondarvr]

Re: Gel coat tinting

For medium colors like Sky blue sometimes you will start with a neutral base and add some white and blue pigment, but only small amouints of each. Other times you may blend white and neutral base together then add blue, both methods keep the pigment load lower.

I read your post and was watching a movie at the same time, so there was a delay between reading it and replying, I forgot you said it was a white base and the color was Sky blue.

 

[series60]

Re: Gel coat tinting

Gelcoat is a poly based product.

Gelcoat is somewhat of a generic name for a material used to provide a high-quality finish on the visible surface of a fibre-reinforced composite material. The most common gelcoats are based on epoxy or unsaturated polyester resin chemistry. Gelcoats are modified resins which are applied to molds in the liquid state. They are cured to form crosslinked polymers and are subsequently backed with composite polymer matrices, often mixtures of polyester resin and fiberglass or epoxy resin with fiberglass.

It will depend on the type of tint you are using. A good epoxy tint will require VERY little product to color. Lots of very good information here: http://stores.ebay.com/Polymer-Products/PIGMENTED-EPOXY-/_i.html?_nkw=gelcoat&_fsub=2252105018&_sid=61010028&_trksid=p4634.c0.m322. If you want some more expert information call Gerald @ Polymer Composites. He is a chemist that has been developing aerospace polymers for 30 years. He will give you great info about how -why - where - and when regarding anything epoxy based.

 

[ondarvr]

Re: Gel coat tinting

Epoxies can be used, but they tend to have poor UV resistance even when pigment is added, so depending on where the repair is located, epoxy may, or may not be a good choice.

99.9999999% of "gel coat" is polyester based, mainly because of the reason listed above.

 

[Woodonglass]

Re: Gel coat tinting

Series60,

True, There are Epoxy based gelcoats, however the majority of boat mfg's use the unsaturated polyester resin based gelcoats when manufacturing their boats. Therefore I made the quoted statement. Since we here on the forum deal mainly with older boats I believe it was appropriate. We have a resident Epoxy expert here on the forum. Ondarvr has been in the industry for 40 years and has seen just about all there is to see when it comes to poly/epoxy boat building techniques etc.

 

[oops!]

Re: Gel coat tinting

HI salty...

as mentioned above...there is lots of ways to get colors......the old robins egg blue...was a common one.....and i hit it a few times by starting with a neutral.

but grind off all that marine tex carp.....if the glass needs to be repaired.....just add a layer or two of csm....then gellcoat that.

marine tex is a great product ......but IMHO....it is just a temporary fix for someone who has never worked with gellcoat before.
Having worked with gellcoat.....and tinted quite a bit....marine tex is not even in my repair kit.

 

[series60]

Re: Gel coat tinting

I think the key in any fix is the preparation.