quick epoxy question

[SUKIE]

Well, I've finally gotten the garden planted and, barring any frost, should be able to rest for a while on that. I'm glueing  the inwales and ready to progress. My question: I have some MAS epoxy which has pumps that are beginning to fail. Can I pour that into the epoxy I got from Graham? The MAS is the same ratio, 2:1.

Also, thankyou Wes for emphasizing the importance of spending the time to true the hull before doing the filets, I'll be doing my best.

[Ken_Potts]

Instead of mixing brands you could measure with cups or a scale to use of the rest of the MAS.  Currently I'm weighing my 5:1 mixes with a cheap electronic scale and I like the result.  Homemade graduated mixing cups are a good (and cheaper) way to go too.  I don't know if mixing brands (of similar ratio) is a good idea or not but I think I'd just use up the old stuff.  There has been recent discussion of using graduated cups but I can't remember which thread.  Someone will hopefully chime in with a link - If not I'll find it for you.

[Ken_Potts]

Found it - http://www.messing-about.com/forums/index.php?topic=6098.60

(look back through some of the previous pages)

[Hirilonde]

Not all epoxies get along well prior to reacting,  Your boat is no place to experiment.  Get some cups or what ever and use up your MAS.  The ratios for mixing any given epoxy is critical, but the tolerances are forgiving of careful visual measurement.

[Tom Lathrop]

We have never had any problem at all by using different brands of hardeners with different brands of resins as long as the ratio of the specific hardener is used.  Resins are very similar but not completely so since each supplier mixes in some additives to change viscosity or penetration.  Accurately weighing volumes of hardener and resins will show the difference in specific gravity.  They ARE different.

Epoxies should be mixed in a ratio of volume, not weight.  You might get away with it but sometimes you will not.  I also have a digital scale but it is necessary to discover the correct weight ratio to use it properly.

The safe thing to do here is to use the MAS separately.  Easier than finding out what will and what will not work.  Any failure in an epoxy mix can be a major problem.

[Randy C.]

Sukie,

If you look at the site that Ken suggests, I bought the cups at an automotive paint supply store. If you go to page 3 of the same site Howard posted a picture of some cups he made up. They look pretty easy.

[Randy C.]

Sukie,

FYI. I bought 10 cups and haven't thrown any away yet. I just let the leftover epoxy dry, then I squeeze the sides and the epoxy flakes right off. Also, I always leave the stir stick in the leftover to dry. When it's dry the stick pulls out the hard epoxy. I don't know how many times I will be able to do this, but so far I've done it several times.

[Ken_Potts]

   Randy,

   The cups wil eventually crack when you're pulling out the "pucks" of leftover epoxy but you'll get a good number of repeat uses before then.

   Tom,

   I hadn't thought of the specific gravity thing so thanks for mentioning it.  Currently I'm weighing the West systems stuff out at room temperature so there aren't wild temperature swings.  If I measure out a known volume of epoxy and hardener to get the actual weight (sounds like it will be something other than 5:1) will I still be okay with the same weight ratio at different temperatures?

[Tom Lathrop]

    Tom,

  I hadn't thought of the specific gravity thing so thanks for mentioning it.  Currently I'm weighing the West systems stuff out at room temperature so there aren't wild temperature swings.  If I measure out a known volume of epoxy and hardener to get the actual weight (sounds like it will be something other than 5:1) will I still be okay with the same weight ratio at different temperatures?

Ken,  Yes that should work just fine.  The weird capacity of containers that WEST uses kind of confuses things but I think I remember that the containers they ship epoxy in are not in a ratio of 5:1.  Also, I don't think they don't say anything about allowing for temperature in their literature and I have never even thought about that before.  I am not going to think about it again either ;D

[Ken_Potts]

  I think I know why West Systems isn't sold in 5:1 ratios even though it's mixed that way.  Whenever I get to the end of one container of resin I have to go buy another one because I still have hardener left and vice versa - A clever marketing ploy because I don't want to let half a can of expensive goo go unused.  One of these days I'll run out of both at the same time and then I'll buy all my goo from Graham.

  Actually I think they're probably just using standard container sizes.