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Thread: Ratio, Fiberglass Resin to Hardener?

  1. #1
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    Default Ratio, Fiberglass Resin to Hardener?

    I picked up a can of NAPA fiberglass resin. It came with the hardener.

    Last night, I did a small test--- approx 2" puddle and then I added liquid hardener around the circumference of the puddle... the problem is that the resin did not completely harden. It gelled up, but was still sticky.

    I'm not sure if I added too much or too little hardener. What's the correct amount?

    Thank you.

  2. #2
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    Quote Originally Posted by 1969vette
    I picked up a can of NAPA fiberglass resin. It came with the hardener.

    Last night, I did a small test--- approx 2" puddle and then I added liquid hardener around the circumference of the puddle... the problem is that the resin did not completely harden. It gelled up, but was still sticky.

    I'm not sure if I added too much or too little hardener. What's the correct amount?

    Thank you.
    I usually mix it in a paper cup and put in a couple drops per ounce. The exact measurement is not real critical but you can't go to extremes without having negative effects.

  3. #3
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    Thank you, Len. I will certainly try the method you described.

  4. #4

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    2% of hardner to resin, too much hardner and the resin will not cure, most resins will change color once the hardner is added, in hot weather u may only use 1/2% and as high as 4% in winter, and make sure u mix well, a teaspoon of hardner to a regular coffee cup and u should be fine, also some resins are unwaxed and will remain tacky this is so u can lay up with out sanding and is a bitch to sand and will gum up the paper, a trick is to place some wax paper over to allow it to cure

  5. #5
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    I use allot of fiberglass resin in custom fiberglass creation (sub woofer boxes, custom center consoles... currently doing a beer pong table for someone ect ect...i can make anything out of fiberglass) and what sounds like what happened with you is you didnt mix it throughly enough. Len is right mix it in a cup and stir throughly. The worst ive seen by adding to much is my work warping due to to much heat created by the resin curing to fast. It should say on the resin can or hardener tube how much to apply. Use paint mixing cups they work great. Dont bother trying to clean out the resin, wait till its dry and just flex the cup it will crack and fall out... I can use the same cup for weeks this way. And if you need more hardener go to napa and buy MEKP hardener they sell it separately. Good luck if you have any more questions feel free to ask... What are you repairing anyway?

    another random thing I picked up... mix fiberglass resin and body filler to a milk shake thickness add both hardeners then mix it all together. Awesome self leveling STRONG filler for fiberglass work in the right applications...

  6. #6
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    I am sitting here half groggy after waking up tired but I think it is 10 drops MEKP (hardener) per ounce of resin.

    Here are a couple more issues with "fiberglass".

    I know the batch code is important because I had a polyester primer NOT cure once and the problem led back to the hardener being too old. This batch code number can be found right at the bottom of the tube where it is vulcanized together. It is just "stamped" in and very hard to read, but it is there.

    >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>
    The batch code is interpreted as follows: The first number is the year, 1=2001, 2=2002, and 3=2003. The second two numers are the month: 05 = may, 08=august. The last three are for internal purposes. With MEKP you would not want to use any that is over one year old. For best results in storage it should be stored in a dark, cool place. I would try to get a fresh batch if I were you. If it is over a year, I cannot say it won't work, but it may take longer, or may not cure completely.

    Secondly, are you working with "Fiberglass" or SMC ("Sheet Moulded Compound")? If the item you are repairing was made in the last few decades and is smooth on both sides it is probably SMC and a little different animal than "Fiberglass". You need to use SMC resin as the good old "Fiberglass" Polyester resin will have a hard time sticking to it.

    By the way, NAPA MARTIN-SENOUR plastic filler and fiberglass products are made by Evercoat.

    Brian

  7. #7
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    Quote Originally Posted by wyzat520
    ...Use paint mixing cups they work great. Dont bother trying to clean out the resin, wait till its dry and just flex the cup it will crack and fall out... I can use the same cup for weeks this way. And if you need more hardener go to napa and buy MEKP hardener they sell it separately. Good luck if you have any more questions feel free to ask... What are you repairing anyway?

    another random thing I picked up... mix fiberglass resin and body filler to a milk shake thickness add both hardeners then mix it all together. Awesome self leveling STRONG filler for fiberglass work in the right applications...
    Thanks for the ideas. I do think I used too little hardener...

    I'm restoring my 1969 Corvette (http://picasaweb.google.com/1fine69)
    when removing the paint I have found a number of cracks, etc., that need to be repaired.

    Ralph

  8. #8
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    Quote Originally Posted by fiberglass jack
    2% of hardner to resin, too much hardner and the resin will not cure, most resins will change color once the hardner is added, in hot weather u may only use 1/2% and as high as 4% in winter, and make sure u mix well, a teaspoon of hardner to a regular coffee cup and u should be fine, also some resins are unwaxed and will remain tacky this is so u can lay up with out sanding and is a bitch to sand and will gum up the paper, a trick is to place some wax paper over to allow it to cure
    Thanks... I used the wax paper method... and also clogged the heck out of my 40 grit on the DA! :o

  9. #9
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    Quote Originally Posted by MARTINSR
    I am sitting here half groggy after waking up tired but I think it is 10 drops MEKP (hardener) per ounce of resin.

    Here are a couple more issues with "fiberglass".

    I know the batch code is important because I had a polyester primer NOT cure once and the problem led back to the hardener being too old. This batch code number can be found right at the bottom of the tube where it is vulcanized together. It is just "stamped" in and very hard to read, but it is there.

    >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>
    The batch code is interpreted as follows: The first number is the year, 1=2001, 2=2002, and 3=2003. The second two numers are the month: 05 = may, 08=august. The last three are for internal purposes. With MEKP you would not want to use any that is over one year old. For best results in storage it should be stored in a dark, cool place. I would try to get a fresh batch if I were you. If it is over a year, I cannot say it won't work, but it may take longer, or may not cure completely.

    Secondly, are you working with "Fiberglass" or SMC ("Sheet Moulded Compound")? If the item you are repairing was made in the last few decades and is smooth on both sides it is probably SMC and a little different animal than "Fiberglass". You need to use SMC resin as the good old "Fiberglass" Polyester resin will have a hard time sticking to it.

    By the way, NAPA MARTIN-SENOUR plastic filler and fiberglass products are made by Evercoat.

    Brian
    Brian,

    Great advice --- I'll check out the date.

    My Vette is fiberglass - not SMC, so the regular polyester resin should work okay.

    Good to know re: Evercoat... I've been using their products for this resto.

    Thanks.

    Ralph

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