How Accurate do you need Epoxy ratios to succeed?

Hey everyone, just wondering what you all think about mixing 1:1 epoxy in very small quantities- say less than 1 teaspoon of each, about 10-15 drops each.

I generally just squirt a small blob of resin on some paper then another blob of hardner of similar size, mix and done super fast. Scrape off with a tiny screwdriver and apply. It does seem that this method works fine, no gooky, sticky or half cured areas as far as I can tell.

But I was thinking that my method is not that accurate as to the necessary 1:1 ratio (internet methods for accuracy are not used- no syringes, no medical cups, no measured circles, weighing, etc...).

So my question is how accurate does this 1:1 ratio need to be to cure?

Yes I could take more time to measure, weigh, etc... and rather than hear about how to dispense these accurately I want to hear about how close the 1:1 needs to be. I am certain there are experts here who could give a great response.

Of course this will not stop anyone.
 
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My (unsubstantiated) opinion is that the ratio doesn't need to be especially precise for DIY applications.

I have a vague memory from several incarnations ago, using an industrial-type epoxy product, with container labeling showing how working time (and cure time) could be accelerated or retarded by changing the mix ratio. I'm inclined to say the usable ratios spanned 1:2 to 2:1, though it may not have been quite that broad.

Dale
 
That's funny.

I've found that if I mix a little bit at a time, I end up with
not enough.

For 1:1 from the tubes I have and read on the labels, to push
out lines of the same length; one inch, two inch etc.

On 1:5 stuff, Marine Tex, is 1 catalyst: 5 resin where you have to dig it
out of a can, directions are pretty specific to not use too much
catalyst or it won't harden or won't harden properly.

I've screwed up once or twice in 45 years of using the
stuff but generally try to do less is more. Add heat if
needed to speed up the process such as a hair dryer,
if a heat gun use sparingly.
 
No NASA precision needed, 10% error (about "eyeball precision) is close enough.
20% to 30% errors (which are gross) will make cured material not that hard or strong (which are not the same) .

I make speakers, and am quite strict when mixing what will be used to glue cone/coil/spider because that is the single most stressed joint in the speaker, is subject to overheating and must be light, but can leftovers, which may be old and not even (because like it or not you will never use exact amounts) are used to epoxy magnets to plates, a much less critical joint.
 

Highfido

Member
2015-11-24 1:56 am
Ratios of epoxy vary. They are designed for ease at 1 to 1. They are designed to be high performance, at about 4 to 1. They also, at four to one, and also longer cure time, makes a rigid fix etc. The quick epoxys, are much more rubbery after cure. Do nt forget to factor in that you may blend in some iron shavings etc, to bolster the fix. Also, with 4 to 1, it is very much suggested, that you WEIGH the ratios. Don't forget to TARE.
 
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My (unsubstantiated) opinion is that the ratio doesn't need to be especially precise for DIY applications.

I have a vague memory from several incarnations ago, using an industrial-type epoxy product, with container labeling showing how working time (and cure time) could be accelerated or retarded by changing the mix ratio. I'm inclined to say the usable ratios spanned 1:2 to 2:1, though it may not have been quite that broad.

Dale

+1
 
There may be some super-critical versions of the stuff, and they may be for super-critical applications, like NASA, but if you go to the store and buy consumer grade glue, the stuff is designed for "close is good enough", so the consumer can actually use the stuff.

If your glob of this and glob of that systems has worked for you, then that is evidence enough.
 
Another thing to consider is the shelf life of Epoxy, especially after it is opened. After about 1 year it will not cure to it's rated hardness. I found this out the hard way by trying to use some 6 year old 5 minute Epoxy that cured to the consistency of Gummy Bears. At least it was easy to peel off and replace withj new Epoxy 2 days later.
 
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Another thing to consider is the shelf life of Epoxy, especially after it is opened. After about 1 year it will not cure to it's rated hardness. I found this out the hard way by trying to use some 6 year old 5 minute Epoxy that cured to the consistency of Gummy Bears. At least it was easy to peel off and replace withj new Epoxy 2 days later.

Shelf life of most adhesives is greatly enhanced by storage in the vegetable tray of a fridge. Well, you have to warm it up to use it, but that's usually more convenient than buying a fresh batch.
 
The critical thing is mixing more so than exact ratio. Mix it thoroughly, then mix it some more. When you think the blending is perfect, mix it again.

Then reread this message and follow its directions again. :D

Then give it a moment to degas (incorporated air to surface and pop) before use. Most of the epoxies we'd be working with have a long working life, so don't rush it.