Measuring Epoxy

[Jim Dodd]

For years I've watched videos of cedar strip builders using "Mustard" pumps to meter epoxy resin and hardeners. I always crinzed, as I've noted in my own experience how inaccurate those pumps actually are !

I started right off buying measured cups from System Three. They worked great !

But being cheap I've gone to making my own. Here's a few tips.
Go for smooth sided, cups, you can scrape the sides easily, as opposed to the rippled sided ones. I believe you get a better mix too.

I've been using cups from Walmart lately, and with RAKA epoxy have not had any issues. One concern is the epoxy degrading the cups. I once left RAKA's epoxy resin in a cup over night. The next day It had leaked all over my mixing station. Some resins are more aggressive in eating up cups. SO experiment before trying this method !!!

I normally mix 9 oz at a time. 6 oz of resin and 3 oz of hardener, this gives me a 2-1 mix. The cups I use are fairly tall, 16 oz cups. To me taller cups give a more accurate measure than wide ones, especially when making smaller batches.

Here's a pic of how I mark my cups.

As always comments welcome !

Jim

 

[Mihun09]

You are retired right? Not necessarily cheap when you have a fixed income that may need to last another 40 years.

 

[Guest]

For years I've watched videos of cedar strip builders using "Mustard" pumps to meter epoxy resin and hardeners. I always crinzed, as I've noted in my own experience how inaccurate those pumps actually are !

I like the convenience of the pumps, although they are not good when I need a smaller amount of epoxy than a single pump of A and B. If I need just a dab of epoxy I’ll eyeball G/flex in the 50/50 ratio. The pumps are handy when I need larger amounts of resin and can just squirt out another pump or two at the end to finish the job.

If the pumps are cleaned occasionally it is easy to check the calibration while doing the hot water or alcohol flush.

http://www.myccr.com/phpbbforum/viewtopic.php?f=49&t=41997

I know some folks who use the measuring cup method have a marked “master” cup and just drop an identically sleeved disposable cup into that and read the resin level through both cups.

I don’t like wasting resin, and don’t like putting on more resin than is needed, so I try to have some project #2 else prepped and ready in case I have an excess of resin pumped from project #1. If nothing else I paint it on the feet of my outside sawhorses.

 

[Alan Gage]

I use graduated mixing cups for larger batches and syringes of various sizes for smaller batches. I can usually get half a dozen uses or more from each cup (or one use if I don't pay attention and let the resin cure). The syringes are probably good for a dozen uses or more.

I used pumps for a little while but I got frustrated waiting in between pumps (took forever for the pump to come back up). Never heard anyone else complain about that so maybe it was just a bad pump.

I like Mike's idea of a marked master cup to eliminate having to mark every cup.

Alan

 

[Canotrouge]

I use the pumps with my west system epoxy for "normal" batch, but if I need really small amount or any amount that are smaller than what the pumps gives me, I use a small scale and it works really good!!

 

[Peach Canoe]

I use West's metered pumps too, and I do as Canotrouge does. From time to time I use my little scale to test the accuracy of the pumps-- should be 5:1 (the ratio for 105/205 and 105/206 is 5:1 by volume or weight).

Also, when I mix up a small batch smaller than a full pump, I use the weigh scale.

 

[Alan Gage]

Lately I've been thinking a scale would be nice. Will have to look into that a little more.

Alan

 

[latremorej]

Another one for a small scale here! I use left over single yogurt cups on the scale for small batches. I haven't had the need for a large batch in a long time as I haven't had the opportunity to do a build. I have made many small repairs and skid plates though and a yogurt cup was all I needed.

Jason

 

[Guest]

Another one for a small scale here! I use left over single yogurt cups on the scale for small batches. I haven't had the need for a large batch in a long time as I haven't had the opportunity to do a build. I have made many small repairs and skid plates though and a yogurt cup was all I needed.

For a small batch epoxy pot I use 2 oz disposable Hefty Mini-Me shot glass cups, especially if I can find them on sale or in Dollar Store pricing.

http://www.walmart.com/ip/Hefty-Mini-Me-Plastic-Cups-Red-20-count/46479569

They are ideal for small batch pumps or 50/50 eyeball mixing with G/flex. They would be even better if they were translucent for use with a marked “Master” cup sleeve.

Back when I had medical supply access I used graduated urine cups and medicine cups, but I haven’t found a similar couple ounce or smaller graduated cup since.

For master sleeving transparency and epoxy resin durability Chinet Cut Crystal cups work well. They are good for multiple resin uses, and enough of the lip protrudes from the master cup to easily grasp. Don’t try to forcible bend them though; the rigid transparent plastic will bend a little . . . .and then crack.

http://www.walmart.com/ip/15723835?...43375552&wl4=&wl5=pla&wl6=78303228992&veh=sem

Anyone have a source for inexpensive 1oz graduated cups?

 

[Peach Canoe]

Here's something from Amazon.

http://www.amazon.com/Non-Sterile-Graduated-Plastic-Medicine-Count/dp/B000IFBFXI

 

[Alan Gage]

Also, when I mix up a small batch smaller than a full pump, I use the weigh scale.

This thread finally prompted me to buy a small scale for dispensing resin. They're cheap and plentiful. I've been using it for 1 1/2 weeks and have been very happy. It's nice not being tied to graduated containers (either purchased or DIY). Now I can finally use all those opaque yogurt cups I've saved.

http://www.amazon.com/gp/product/B004164SRA?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00

Alan

 

[southcove]

This is a little bit off original topic.

What are people finding is the practical storage life for larger containers (opened) of resin and hardener?

I have a nice amount of System 3 that I put away (forgetting to take out the metering pumps, so now need to see if those can be revived?) about 1.5 years ago on a dark shelf...the hardener looks darker and I am going to mix up a sacrificial batch in any case just to make sure it hardens up properly. Making up a couple of 1/4" ply camping boxes for my son and his friends trek this summer and between coating and making fillets and taped corners, will just about finish it off I think.
(thanks Alan for that link to the cheapo scale, was thinking a $40 scale at West would be a real waste for my needs)

 

[Peach Canoe]

From System Three website:

"All solvent-free epoxies have essentially unlimited shelf lives so long as they are stored in sealed containers. The resin may crystallize or the hardener may darken but this does not affect its performance. If the material is more than a year old do a test to satisfy yourself that it cures properly."

The pumps can get a little plugged up after some months in the can, but it's easy to clean them out with acetone or white vinegar. Perhaps putting some tape over the nozzles may preclude contamination during long-term storage.

 

[Guest]

I have a nice amount of System 3 that I put away (forgetting to take out the metering pumps, so now need to see if those can be revived?)

Pump cleaning instructions per West System in link in post #3 above. Easy peezey and a good chance to measure check the calibration.

 

[southcove]

Good stuff, thanks for the reminders. What was of some interest on first posting, quickly forgotten over the weeks intervening. Brain acting like one of those stuck pumps...

 

[jmhockey23]

After reading this, I tried a few batches using a scale and they turned out fine. Then I went and read more about using a scale and found some people that cautioned the use of scales due to the resin & hardener having different "specific gravity" levels. Meaning a fluid oz of one may weight differently than the other. I threw two sealed gallons of Raka on my scale and they were indeed different something like 8lbs 3oz to 8lb 14 oz. Certainly their could be an error in this method and I haven't tried measuring exact amounts and weighting yet. The few batches I made using the scale worked great due to the convenience and they turned out fine... Now I'm paranoid though.

 

[Alan Gage]

After reading this, I tried a few batches using a scale and they turned out fine. Then I went and read more about using a scale and found some people that cautioned the use of scales due to the resin & hardener having different "specific gravity" levels. Meaning a fluid oz of one may weight differently than the other. I threw two sealed gallons of Raka on my scale and they were indeed different something like 8lbs 3oz to 8lb 14 oz. Certainly their could be an error in this method and I haven't tried measuring exact amounts and weighting yet. The few batches I made using the scale worked great due to the convenience and they turned out fine... Now I'm paranoid though.

The mix ratio by weight certainly is different than the mix ratio by volume. Most epoxy manufacturers will give the mix ratio of both in their spec sheets. I couldn't find the volume measurement on RAKA's website but a little internet sleuthing turned up 100 parts resin to 42 parts hardener. So if you poured out 3 ounces of resin you'd multiply that by .42 to determine how much hardener to add (1.26 oz).

I've really been liking my scale; haven't used a syringe since I got it. 1/2 ounce batches aren't a problem.

Alan

 

[jmhockey23]

The mix ratio by weight certainly is different than the mix ratio by volume. Most epoxy manufacturers will give the mix ratio of both in their spec sheets. I couldn't find the volume measurement on RAKA's website but a little internet sleuthing turned up 100 parts resin to 42 parts hardener. So if you poured out 3 ounces of resin you'd multiply that by .42 to determine how much hardener to add (1.26 oz).

I've really been liking my scale; haven't used a syringe since I got it. 1/2 ounce batches aren't a problem.

Alan

Thanks for the info! Yeah, just found a few different posts out there specific to Raka.