# Gelcoat and MEKP ratio issue



## FSUDrew99

So bought a quart of MarPro gelcoat with wax with the MEKP hardener included. Manager at store told me to run 10-12 drops per oz of gelcoat I mix up. Well it was not cured this morning after applying it last night which is either one of two things old hardener that came with the gelcoat or not enough hardener. 

Prior to the gelocat I mixed some silica, resin and a different bottle of MEKP and it flashed in no time with the same ratio of 10-12 drops per oz. 

Can someone chime in as I am not going to take off the gelocoat on the repaired areas with acetone and start over. Sucks.


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## FSUDrew99

Found this too....


Must be the catalyst being old idk... Calls for 10 drops per oz as well.


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## firecat1981

Mekp is too hard to measure by drops to me, so I use a syringe and do it by ml instead. I don't know if age effects it or not. 
I've tried rolling properly mixed resin over some that didn't properly cure in the past, it will harden, but won't be as strong or last as long.


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## FSUDrew99

I used acetone and sanded off the old gelcoat. I used the other MEKP and it seemed to be working and got a tad bit on my skin and could feel it burning a little. The gelcoat set up what was left in the mixing tub before I threw it out. 

It still looks a little wet, but it hopefully will set up over night. I did not cover it due to it having wax in the gelcoat as well.


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## devrep

The stuff I have is 19 drops per oz.


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## DuckNut

Gelcoat can take as much a 2x the amount of MEKP as resin. 

In your above statement where you got it to kick, was that gelcoat or resin with the other stuff added in?


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## FSUDrew99

DuckNut said:


> Gelcoat can take as much a 2x the amount of MEKP as resin.
> 
> In your above statement where you got it to kick, was that gelcoat or resin with the other stuff added in?



I just applied with with 11 drops per ounce to the 2nd batch of gelcoat and the mixing tub I used started to harden up. Granted a few hours afterwards I checked that mixing tub and it was all solid but still soft. I would assume it would be rock hard by now. 

I'm gonna be pissed taking off the gelcoat again and reapplying if that's the case tomorrow am when I check it. 

I was thinking about adding even more MEKP but was worried it would have a reverse effect possibly.


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## DuckNut

If you add too much then you risk it burning. Turning brown or even worse your mixing jar catching on fire.

Try one more 1 oz batch and add 20 drops and see how that does.


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## FSUDrew99

DuckNut said:


> If you add too much then you risk it burning. Turning brown or even worse your mixing jar catching on fire.
> 
> Try one more 1 oz batch and add 20 drops and see how that does.


Went out to check it this morning at 7 am. Note I applied the new gelcoat with different MEKP bottle at 11 drops at 2pm yesterday.... still gooey in some spots on the surface. Mixed for a full 2 mins.


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## firecat1981

Again I'm not a fan of "drops" because its super subjective. How do you know how many ml's per drops you are getting? I would forget the drops and using ounces. Get a proper measuring cup and syringe and use cc's or ml's for both. Mix in the MEKP at 1-1.5% and see if it works ok on a test panel. Polyester resin is not nearly as forgiving as epoxy so you really gotta be on the money with the mix.


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## FSUDrew99

firecat1981 said:


> Again I'm not a fan of "drops" because its super subjective. How do you know how many ml's per drops you are getting? I would forget the drops and using ounces. Get a proper measuring cup and syringe and use cc's or ml's for both. Mix in the MEKP at 1-1.5% and see if it works ok on a test panel. Polyester resin is not nearly as forgiving as epoxy so you really gotta be on the money with the mix.



I am going to shoot for 2% ideally. Talked to a local gelcoat guy locally who does good work and he tells me that he would shoot for 20 drops as that should do it.

I don't know the exact number of CC's or ml's per ounce of gelcoat. Even the stuff I have found online calls for typical 10 drops per ounce.


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## firecat1981

That's the problem. Depending on the orifice size of the bottle your using 10 drops could equal .5cc, 1cc, 1.5cc..... using a $0.89 syringe is cheap insurance to me.


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## FSUDrew99

firecat1981 said:


> That's the problem. Depending on the orifice size of the bottle your using 10 drops could equal .5cc, 1cc, 1.5cc..... using a $0.89 syringe is cheap insurance to me.


So the real question is what would my measurement in ml or cc for one ounce of gelcoat...???


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## firecat1981

1 fluid Oz equals about 30ml if memory serves, so if you want 2% you would need 0.6ml of MEKP per oz of gel.


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## FSUDrew99

Found this chart:

This 2% ratio equates to about .625 CC per ounce of gelcoat. If one CC is roughly 30 drops as stated below that would put me at roughly 18.75 drops of MEKP per ounce of gelcoat. If this is true which seems to be the issue I would be almost at half as much as I need being I put 11 drops per ounce of gelcoat versus 18-19 drops.


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## FSUDrew99

firecat1981 said:


> 1 fluid Oz equals about 30ml if memory serves, so if you want 2% you would need 0.6ml of MEKP per oz of gel.



Looks like our calculations were right on with each other. Ill just get a syringe and shoot it then or I guess I could do 20 drops as well. I'm sure the syringe will be more accurate though.


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## FSUDrew99

Mixed 3 new ounces of gelcoat and put between 1.8-1.9 cc's (0.625 cc's per oz) of MEKP in the mix for two minutes. Let's hope this works this time!


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## permitchaser

Man I hope its working. I always go way over the amount needed.


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## FSUDrew99

permitchaser said:


> Man I hope its working. I always go way over the amount needed.


It already looked better an hour after applying. I'll try and touch it in the am. When it was the bad batch it stayed shinny, after an hour with the doubled up MEPK it already had all the sheen to it gone. I'll know more in the am.


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## FSUDrew99

Good news! With the new ratio of .6 CC per oz of gelcoat everything took perfect. This morning not even tacky and hard enough to sand already! Thanks for the help @firecat1981 . No more droppers for MEKP in my future haha.


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