mixing polyester resin

Hey guys, I’m a first time board maker and have recently finished shaping a 9’1" nose rider and was really happy with the result :slight_smile: My attempt at glassing was not so good! I mixed the polyester resin and MEKP hardener @ 1% which I thought would give me plenty of time to glass the bottom of the board. It went off like a rocket and only gave me about a minute before it was all over! Unfortunately I now have 2 areas on the board with blue tinted resin where I placed my logos…that as far as it got. Now have to try and repair the board for another go at it…not happy ) : My supplier has given me a slower catalyst to try, hoping this works. I watch these guys glassing boards on Youtube with up to 10 mins working time, am I doing something wrong? Any advice or tips would be greatly appreciated. Cheers…Brenden

Here’s a couple of pics…I didn’t get far! Managed to get the tail logo off, no luck with the main one.


you need to have everything ready aka glass cloth already pre cut and layed out across the board. if you want to put labels on roll back that small part of the coth back then put it back over your label. glass the bottom let it kick then glass the top of the board. heat is a huge factor when glassing if it is too warm your ratio needs to be lower also might want to check your math because i think 1% would give you more than 1 minute work time. an easy mixture ratio i used to do when first glassing was 7mL to every 30 ounces. if you need alot of time you could even run only 5mL to every 30 ounces. once you get better and have more resin time under your belt it is easy to play around and adjust ratios to speed up or slow down working time. if you have access to uv activated powder and can glass then move your board into the sun maybe try that. goodluck

Thanks for the feedback Jcyr, much appreciated. I did have everything ready as you suggested, mixed 10ml : 1 litre and it went off really quickly? I’m now looking at the best solution to move forward. Do you know anything about foam staining? I wonder if I could continue to add a few different colours or shades of colour to the foam before glassing with a clear resin? I can’t find too much info on the process and it’s not what I intended…really wanted to do a transparent blue tint top and bottom. I do have some Q Cell that I can use if needed to repair any damage caused if I try to sand back to raw white foam again. I ensure that I glass in the cooler part of the day next time…I think that may have had a big part in my demise.

Your supplier has given you slower catalyst to try… huh???

Please explain.

Ps…

If you kicked poly resin fast enough to go off in 1 minute and you mixed enough to glass a whole board with and only used that small amount on your board the rest that was in the bucket would have probably caught fire.

Definitely would have been smoking and hissing and cracking like crazy.

Leave it as is put a logo over that blue spot on the bottom glass the whole thing clear. USE UV CURE Laminating resin

Wideawake-like this?

Agree wit WideAwake. That bucket of resin would have been seriously hot to the point of smoking and not being able to hold the bucket.
I am however pretty impressed with your gung ho’ness to go so complete as to do a resin tint and place logos on your first board. Those are some lofty expectations. I was just happy to make sure the resin kicked and I got the glass completely saturated and lapped around the rails on my first few. I have done a handful of boards and still have not even got around to pretending I am a company with a name yet. I just want the basics and to make people smile when I hand over their new board I have worked so hard on.
This is nothing against you. I applaud your efforts, but If I could suggest anything, it would be to slow down and make sure you have all materials ready and cut. Make sure any tools you may need are within arms reach and that you know you can just put all your focus on the glassing aspect and not the tinkering with tools and reaching for things during the process. You need all of your time to work before it kicks. Welcome to the club, where things happen and you have no idea why. We have all been there.

It was red hot, didn’t burst into flames, but I certainly couldn’t hold it. I’m still learning Wideawake so can’t explain the slower catalyst? I didn’t see the brand that my supplier has given me this time round, but he said it would give me more work time and has actually written on the container “slower”?? I’ll be sure to ask next time I see him. Might take your advice Bud, sounds like the best option. Thanks Guys…

J - EXACTLY! Photo made my day!

Ritchie - the speed at which poly resin kicks is determined by the amount of Mekp you add. - unless you supplier gave you something laced with cobalt. - call and ask them the difference between what they sold you.
Is this a surfboard supply warehouse?

Always keep a 5 gallon bucket of water near by to dump extra resin into.

my first board was a mess. It was during a hot Spanish summer, and I used 2% MEKP it took like 5-8 min till the resin turned to gel.
Then I found out about the UV powder.
Now what I do is foam stain and glass with no tinted resin. The UV resin gives u plenty of time (I use to do it in around 30-45min). And it’ll get hard just when u expose it to uv.
UV resin is the best way to get use to the lamination part.

A pic of the MEKP container that says ‘slower’ please.

Bud…he filled the normal MEKP container with what he referred to as a slower catalyst and wrote on the container “slower” with a marker. Not sure of what exactly it was, will find out next time I’m there. I dropped into a local board marker here on the Sunshine Coast in Queensland today and have organised to sit in on the lamination process next week. Really good of them to be ok with me doing this…only cost me a bottle of red wine. The guy I spoke to talked about how he mixes up an initial batch of resin with only a couple of ml of catalyst, lays the glass in and then finishes off with another batch of resin with a higher % of catalyst to kick it all off. I think I’ll learn a lot by watching pro at work!

Just remember some of the things the pros do are to speed up the process not make it easier for them… they are pros and have no questions during their process. Good on you for learning but be warned a two batch lam in poly is tricky

I mixed my first batch of poly resin some time around 1964. In the ensuing 52 years I have never once heard reference to “slow” catalyst, until this post. I think It’s safe to say there’s no such thing. Poly resin is not like epoxy, where you have a two part system with a closer ratio.
I think it’s a safe bet that you measured your MEKP incorrectly. A 1% amount of catalyst should give you a lot of work time, unless you’re trying to glass in scorching hot air temps, in direct sunlight.
I have a feeling there was a misplaced decimal point in your measurement. What you describe sounds like a batch with 10% catalyst, not 1%.

There is a slow version of Mekp but it’s not typically associated with poly resin. Nor have I ever heard of anyone using it to build a poly board…

The slow stuff is used with vinylester resins… Don’t know all the details but I believe it helps to reduce foaming. Also not sure if it has some other stuff in it or just formulated a bit different. Nor do I know how much slower it is or why it’s slower, just that it’s referred to as slow and not regular.

If you got your resin from a boat supply warehouse they may very well have given you the VE catalyst.

I am still on the miss measured train aswell.

I don’t have it handy, but I believe the old “Surfboard Building” book (the one that was in English/Japanese) mentioned a couple grades of MEKP being available. Mind you, I’ve never had access to more than one grade, but it is feasible that our friend has been given an alternative. No doubt watching a pro work and being able to ask him questions will prove invaluable. He’s also closer to the source and may have insight as to what went wrong.

1000 ml = 1L and 10 ml = 1% of 1000ml (1L)

I think is better to use a precision scale, due that 1L of resin is 0.9 kg and he has to add just 9 grams of mekp (around 5ml)

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The supplier I purchased my gear from sells all sorts of fibreglass materials, but he is a ‘surfboat’ builder so you might be onto something there Wideawake! As far as my mixing the wrong ratio…I have checked and double checked, it was definitely @ 1% (10mls : 1litre). The only other thing I question is that the two tins of resin I used had a different appearance. By this I mean one had a blue tint and the other had a green tint. I mentioned this to the supplier and he said it was not an issue probably just resin from different manufacturers? Hope one wasn’t UV resin or something strange like that, certainly wasn’t marked as such? It was fairly warm during the day when I tried to glass the board, I’m learning quick that this was probably not my best option.