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Thread: Mixing West Marine Hardeners

  1. #1
    Join Date
    Feb 2018
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    San Francisco, CA, US
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    Default Mixing West Marine Hardeners

    Hello everyone, first time poster here.

    I'm sure the simple answer is "Why would you do that? Just don't", but from a chemistry perspective, can anyone speak to the consequences of mixing West Marine 205 Fast Hardener with 206 Slow Hardener, in even proportions, assuming I still maintain 5:1 with the WM Resin? If I maintain temperature above the 60 degree threshold for the slow hardener, my under-informed guess was the complication would be curing time. I'm curious if the net effect would be an averaging of the two, or if somehow this would interfere with the curing altogether and result in a botched cure? Does anyone know this for sure, or is it just a matter of "don't mess with resin"?

    The reason this came up was I was midway through a fiberglassing session and realized I was running low of slow hardener. I go through so much more resin than hardener, I just forgot to check the latter before starting! I figured I had enough slow hardener left for ~2 modest pots. I was faced with either switching to Fast hardener, which I really don't like doing (time pressure!), or stopping for the day.

    ...OR, I could try making a hybrid of the two, getting me ~4 pots, and through my plan for the day.

    I opted for caution, called it quits, and resolved to immediately go home and ask the internet if it would have worked

  2. #2
    Join Date
    Jan 2000
    Location
    Portland, Maine
    Posts
    15,940

    Default Re: Mixing West Marine Hardeners

    I think you could do it but I’d call West System’s tech help line just to be sure. They are very helpful. But don’t call West Marine. They don’t make epoxy, they are just a retail store. West System Epoxy is made by the Gougeon Brothers.

  3. #3
    Join Date
    Dec 2003
    Location
    Portland, Oregon
    Posts
    46,297

    Default Re: Mixing West Marine Hardeners

    One can mix different speed epoxy resin hardeners in whatever ratios you wish. The speed will change per the ratios used. Half 'fast' and half 'slow' would cure almost in the middle between the two. As long as you keep to the same ratio (5:1; 2:1, etc.), you can likely mix hardeners from different manufacturers. Probably none of them would recommend it... but I doubt you'd have problems.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  4. #4
    Join Date
    Dec 2006
    Location
    Tuckahoe
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    7,848

    Default Re: Mixing West Marine Hardeners

    read this if you have not already.

    https://www.westsystem.com/the-gouge...-construction/

    an axcellent resource.

    then read this for the authoritative answer to your specific question.

    https://epoxyworks.com/index.php/mix...ystem-epoxies/

    i have done this before to acheive a medium fast or medium slow cure with good results.


    welcome to the Wooden Boat Forum; beware the Bilge.
    Steve Martinsen

  5. #5
    Join Date
    Apr 2014
    Location
    Anchorage, Alaska
    Posts
    230

    Default Re: Mixing West Marine Hardeners

    I prefer your choice of "calling it quits" because boat building is my hobby for low stress relaxation so I avoid the hurry. Plus, I find my wood work to be of higher quality when I go slow and relax.
    Last edited by Mo 'Poxy; 02-05-2018 at 10:30 PM.

  6. #6
    Join Date
    Feb 2018
    Location
    San Francisco, CA, US
    Posts
    6

    Default Re: Mixing West Marine Hardeners

    Thanks everyone!

  7. #7
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
    Posts
    14,385

    Default Re: Mixing West Marine Hardeners

    Its no problem , I do it regularly.
    Read the book.

  8. #8
    Join Date
    Jul 2011
    Location
    Lindstrom, MN
    Posts
    1,956

    Default Re: Mixing West Marine Hardeners

    Quote Originally Posted by David G View Post
    One can mix different speed epoxy resin hardeners in whatever ratios you wish. The speed will change per the ratios used. Half 'fast' and half 'slow' would cure almost in the middle between the two. As long as you keep to the same ratio (5:1; 2:1, etc.), you can likely mix hardeners from different manufacturers. Probably none of them would recommend it... but I doubt you'd have problems.
    I agree, but I would not recommend it. Within one brand, you can mix hardeners with the same mix ratios, but between brands, things may not match up well. The number of epoxy groups in a given amount of resin has to equal the number of amines in the hardener. It is hard to get the information from most manufacturers. I suspect that most epoxy resin have similar epoxide equivalent weights, and the amine values (amine hydrogen equivalent weights) vary with the mix ratios. If that is true, then you can mix and match different brands. The price of a half can of leftover hardener is small relative to the mess it it doesn't work.

    There is a number for the resin, the epoxide equivalent weight, and for the hardener there is the amine hydrogen equivalent weight. If you can find the numbers, you can calculate the mix ratios.
    You can read about this here on page 9 http://www.huntsman.com/performance_...theramines.pdf
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

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