How do you measure 2-part epoxy?

I use the West System G-Flex for handles. The most important things to remember with epoxy are:
1 - Proper weight (or volume) for a mix, with the G-Flex it's 1:1 by volume
2 - Proper mixing, I mix for at least 2 minutes, even in a small batch for knife scales, scrape the sides of the cup & the bottom (1 oz. medicine cups)
3 - Surface prep, epoxy won't stick to oily surfaces, dirt or scaly stuff. Acetone, sanded bare metal & cleaned again will always work. Coarse scratches help epoxy key into the surface.

I know this is pretty basic stuff, but each step is very important for a good bond. The better, flatter & cleaner the prep, the better the bond. I also use mechanical fasteners for my stuff (screws, pins & tubes) to anchor things in place, since I'm new to knife making. It's the basics which make epoxy work or fail, not rocket science, but it needs to be done right. Wear nitrile gloves, as allergies to this stuff are cumulative & will sneak up on you. Avoid starved joints, don't over-tighten to push it all out before there's a bond.

I see some guys who get in a hurry on FIF & have this stuff running off of bare hands & all over the knife, makes me cringe, it's just not worth it! There's some truly weird chemistry involved with this stuff.
 
I dont know, but something seems amiss here. I,( as have most of you!) have been measuring out epoxy for (well, a long time).... never weighed it ... just “eyeballed” it (as others have said). Sometimes i have more resin, sometimes more hardener ... but never has the stuff failed to harden. I have to believe there is a pretty wide margin of error for the ratios of the two? For the OP to have his resin remain gummy means his ratios were WAY off, or something else is going on..... ?

at work i have seen resins not cure due to bad mixing, so as one other had said, mix well! Otherwise maybe the resin was not given enough time to harden, or it was really cold and thus did not cure, or it was “bad” (old or stored under bad conditions)? Mostly just guessing here...
 
Hi @CushingH. Since you authored a recent epoxy mega thread (highly recommended and very sciency) maybe you would know if the very large volume of JB Weld the OP is using in a drilled tang hole (as opposed to a slot) requires additional cure time? He can easily mock up a test for this. His hole is likely in the 1/2" range unless the tang stick is tiny. I recently drilled pith out of an antler and replaced with a slotted dowel as recommended by others here, greatly reducing the volume of epoxy needed.
 
John Cahoon said:
Hi @CushingH. Since you authored a recent epoxy mega thread (highly recommended and very sciency) maybe you would know if the very large volume of JB Weld the OP is using in a drilled tang hole (as opposed to a slot) requires additional cure time? He can easily mock up a test for this. His hole is likely in the 1/2" range unless the tang stick is tiny. I recently drilled pith out of an antler and replaced with a slotted dowel as recommended by others here, greatly reducing the volume of epoxy needed.
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I would think the increased volume is a non issue. Epoxy cures faster when warm, and the hardening process actually produces heat - a large volume will not cool off so easy, actually get warmer, and cure faster - does that make sense?

samples of metal undergoing cross section analysis are regularly “potted” inside of hockey-puck size volumes of epoxy, with no trouble with the epoxy hardening...
 
I do my best to get close to whatever ratios are required by the type of epoxy I am using, but I am in no way perfect. It does seem like there is some wiggle room. I worry more about really getting a good mix(scraping sides of container+stir stick, stirring lots) and cleaning surface of material. Temperature makes a difference. You are going to get a different cure time if you are in a 50 degree shop or a 75 degree room.

Also know that heat is produced as the epoxy cures. Different types produce more heat that others. I was working on a large burl slab and had a soft spalted area that I used a product called "Rotfix" on to harden that area. I used a large amount of Rotfix and poured it into the area which soaked it all up. A minute or so later there was "steam" coming out of the area. I couldn't understand...the slab moisture content was 10%. A minute or so later I realized this was smoke!!!! Not being the sharpest tool in the shed I poured the rest of my mixed container of rotfix onto it to drown whatever was on fire inside my slab. Smoke stopped for a second and then started up again. It was 2 am and the slab was 300 pounds. Not moving it and no one is going to answer on the woodworking forum!!! Significant smoke...I grabbed the cat's bowl of water and poured it on. Got more water and poured it on. At this point I was more interested in keeping the thing from bursting into flames. Once I got the smoke to stop I was worried it would start again. I was worried it would start again so I opened the garage door and got most of the smoke out, grabbed the smoke detector and sleeping bag from the basement and set up in the garage with my respirator on and slept til 7am to make sure it didn't light up again. My point is there can be a lot of heat and it is smart to read the product sheet!

I have read threads discussing solvents and residue. It seemed like a lot of people with more knowledge than me said that acetone and lacquer thinner still left some residue albeit not much. But best practice was methyl acohol. In Canada I buy it as Methyl Hydrate....I can't remember the name the USA guys were calling it.
 
Your story had me laughing Randy - though I am sure you were not laughing at the time. you just told it so well!

Yeah - a lot of "common" materials give off heat when cured. Concrete being one of them. when they poured the Hoover Dam, they had two major engineering challenges. One was to find a way to pour it **continuously** from footings to top (seams in the concrete being a Really Bad Thing in a structure like that . The second was how to control all the heat generated as the concrete cured (and there is a LOT of heat). they actually built a large refrigeration plant on-site, and as they poured the concrete. simultaneously inlaid refrigeration coolant pipes inside of the concrete (not really sure whether they just ran cold water from the river through the pipes, or whether they actually used active refrigeration.....). If they had not done that, the concrete would have heated up and, at best, cracked, at worst it could have "exploded" from the internal stresses....
 
I use the system 3 clear coat for a lot of stuff and I use graduated cups and mix with glass rods. I weigh out the epoxy in a scale and use the ratios provided by the manufacture. Depending on the volume needed I have 2 scales. One bigger one for larger volumes and another lab scale that can measure the weight of an eyelash. Another thing I have that’s handy is an epoxy gun from 3m that takes the double barrel cartridges and I dispense it through a mixing nozzle. After a quick prime she is good to go and makes doing hidden tangs super easy. You just squirt it into the hole and done.
 
Interesting that larger volume of epoxy doesn't need longer time to cure.
I have an unheated garage shop. I heat up a cup of water and sit my resin and hardener in hot water to get warm and thin out. After mixing, the warm glue flows well into nooks and crannies, but I let it cure in the cold overnight (maybe 40 degrees F). This has worked well in the past, but maybe I need more than 24 hours? Or is this just too cold?

Another point is that I currently color my glue black with laser printer toner, a very fine polyester powder. I assumed polyester will mix well with epoxy resin. I do mix well, to get the powder color and the hardener fully blended.

I've been drilling round holes for hidden tangs, maybe 1/2 inch diameter. Maybe I will try gouging out a slot, I have a Sawzall blade that I made into a thin scraping tool. Another option is to try burning a red hot tang into the handle block, as seen on Forged in Fire.
 
By far the best way to clean tangs of blades for glue up is with a solvent. But there is a trick that I never considered till I was watching a YouTube guy talk about industrial part cleaning. In big industry how do you clean parts without wasting tons of solvent. What I found out is you have a container that can be heated. I have a glass lab vessel that necks down. I clean the tang good with a rag to get anything like dirt or hunk off. Then I put ethanol in the glass and heat it till it’s steaming. I then hang the blade in the vessel. What happens is the solvent condensates on the cold blade and runs off taking any oils or other stuff with it. It is then turned into vapor again and recirculates leaving the gunk in the bottom. The guy was saying that if you want a perfectly clean surface (for building electronic displays and electronics) you can not get this with wiping as your just smearing stuff around.
 
Jt - yes,many industrial cleaning processes use hot solvent vapor (i used to use a similar process wayback when when iwas making circuit boards.

PLEASE BE VERY CAREFUL IF/WHEN USING YOUR HOT ETHANOL PROCESS. First, ethanol vapors can be breathed in, and will make you drunk far faster than drinking the stuff (dontask me how i know) and if you are using denatured alcohol, there are toxins that you will breath in also. Also, ETHANOL VAPORS ARE EXTREMELY FLAMMABLE. When you do what you describe, you could ignite the vapors, and they might well flash back to the container, and ... BOOM. you are basically handling a steaming hot Molotov Cocktail. I strongly recommend you do NOT do this.

(BTW - the folks who try to make their own Meth use a similar hot extraction process with a flammable liquid. There is a reason it is not uncommon to hear of them suffering third degree burns ......)

(the industrial processes are tightly controlled, very well ventillated, and most often use non-flammable solvents
 
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Another thing not to do, is don't put acetone in a plastic cup. When you pick it up, you get the sides, but the bottom stays down and all the acetone runs out.
 
kbright said:
Another thing not to do, is don't put acetone in a plastic cup. When you pick it up, you get the sides, but the bottom stays down and all the acetone runs out.
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Same thing with epoxy in a solo cup!!
 
Kbright, don't let epoxy cure in the cold. Epoxy+cold=bad m'kay
I always take whatever I'm epoxying in to the house to harden in a warm room.
 
Hengelo_77 said:
Kbright, don't let epoxy cure in the cold. Epoxy+cold=bad m'kay
I always take whatever I'm epoxying in to the house to harden in a warm room.
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Most epoxy's come with a data sheet and give you min/max temperatures for curing too. It helps a ton to follow what they say. One bar top self levelling epoxy I used said minimum temp of 78 degrees. On the forum part of their website there was a thread that showed example after example after example of fails when customers didn't follow the temperature instructions.
 
One “little” trick is to put the thing being cured into a “low” oven (maybe 120 - 140F). Cures fast and hard. Done in industry all the time. (But best to follow any max temp restrictions on the specific epoxy). Arrhenius equation for those that might be interested in such things. :-).
 
I was given a tip to put curing parts in a cardboard box with an incandescent light. In cold regions some people hang a light bulb under their engine block so the motor oil doesn't get too thick. That's old school, most people have a heated dipstick now.
 
I was not heating with an open flame, and it was just hot enough to cause it to start to condensate on the cold blade. It was just done as a test to see about building a dedicated set up.
 
JTknives said:
I was not heating with an open flame, and it was just hot enough to cause it to start to condensate on the cold blade. It was just done as a test to see about building a dedicated set up.
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That helps, but I would still be very cautious about the approach.
 
tim37a said:
Go to the local feed store and get two plastic syringes. Fill them with part A and part B and put a piece of masking tape on each one with the A and B written on the tape with a pen. Squirt out the required amount of each in a non-waxed cup and mix. Leave the unused epoxy in the syringes. When the epoxy is used up, clean the syringes with acetone and refill with epoxy.
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This is a great bit of advice! I've always used syringes, but didn't think to use two and keep epoxy in each. Great way to reduce waste.
Acraglass has been a great epoxy for me. I gave up on the standard equal part epoxy long ago and never looked back.
 
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