Small Batch Epoxy Mixing

[mower]

I've always had a problem mixing small batches of epoxy. Maybe one of you have a simple solution. When I use an epoxy brand that uses other than 1:1 ratio, and does not have those convienient pumps, I usually use paper cups for mixing. Two cups of resin, and one cup hardner etc. However, for a very small repair, when I want less than one cup, I always end up making adjustments because the cups I'm using are bigger at the mouth than at the base, and therefore the top half is considerably larger than the bottom half. Occasionally, I have got the ratio wrong. What do you do to overcome this problem? Don't tell me to buy another brand of epoxy with a 1:1 ratio, I've got loads of a 2:1 brand left over.

[On Vacation]

Very small amounts can be done with tablespoons or measuring spoons. Find you two of the same size and keep one for the epoxy and one for the hardner. Jigger glasses work also.

Make sure that you mix it in a small enough container that you will get it all mixed up. What happens in many times, some of the substance will stick to the side of larger containers and will not mix properly. Also, clean off the stirring stick while you are stiring to allow the mix to run back down into the container to be mixed into the overall liquid.

[ 03-14-2003, 10:00 AM: Message edited by: Oyster ]

[NormMessinger]

hypodermic seringes (as Donn to spell it) from the Vet supply store or System Three.

[Paul Scheuer]

For very small batches, I lay out equal or proportionate beads of the components on a pallet. Easier to do when the components are sold in tubes.

For middle sized, small batches I use the catsup cups from McDonalds.

[Scott Rosen]

Almost all of my epoxy batches are small.

I use the 50ml beakers from Jamestown Distributors. They are marked in 5ml gradients and are accurate enough for a 2:1 epoxy.

Beakers (http://jamestowndistributors.com/cgi-local/SoftCart.exe/store/entries/index_paint_supplies.html?L+scstore+bxyl8342ffa1ff a1+1067172443)

[Bruce Hooke]

Well, first off I wouldn't bother with an epoxy brand that doesn't include a reasonably dispensing system. In my mind that's a false economy because of the wasted time and increased error rate that results. That said, as an occasional cross-check against my pumping system I use an accurate scale to measure the epoxy, and a scale would work just as well for mixing small batches. You do, of course, need a precision scale, but I also use the scale for things like measuring wood samples to work out the moisture content before and after oven-drying a sample.

[Figment]

I'll second the thought on the beakers from Jamestown. Even with the pre-ratio'd (don'tcha love inventing words?) pumps, it's difficult to accurately guage a half-pump or a quarter-pump. using those plastic graduated beakers has saved me a LOT of wasted epoxy.

[Dan McCosh]

I've used lined measuring cups available in the paint dept. at the hardware store. You can use just one, fill to the appropriate lines with resin, then hardner, then mix.

[JimConlin]

Seldom do I mix a batch of less than one squirt of the Gougeon mustard pumps (about 1 oz.). If i have several tiny jobs to do over a period of an hour or so, i use slow hardener and put the cup someplace cool between applications. Sometimes it'll wait for me.
I have a cooking scale that reads down to a couple of grams and has a 'tare' feature which deducts the weight of a cup. It's fussy, but i suppose that you could measure a batch as small as, say 15 grams with moderate confidence of the accuracy.

How much work is it worth to save 20 cents worth of epoxy?

[Sailman58]

MAS epoxy uses a 2:1 ratio, maybe you could use or adapt a set of their pumps. Also, if you use a straight sided container, you can mark the side. 1/4" and 3/4" from the bottom would be a 2:1 (actually 1:2 in this case) ratio.

[JimD]

Lots of places sell small graduated disposable cups for measuring small amounts, no need to order through a distributor such as Jamestown if that's not convenient for you. I just buy them locally

[frameshop]

Jamestown distributers sells small 1qt containers( cat# ps1pp, page #134 current catalog) with good markings on the side. I use them all the time for small batches and have had no problems. Some even have ratio mixes on the side. Roger

[Concordia..41]

In the baby stuff isle of any grocery store you'll find a collection of small measuring syringes and spoons. I like the syringes that are designed to meet out small amounts of cough syrup. I figure that's about the right consistency.

[John Blazy]

Scott and Figment have come close to the easiest method. Use clear film containers. I've been using them for years, over and over with no problems, vitually no inaccuracy for West 5:1. the Fuji film container is translucent and best of all it has straight sides for even graduations that you mark out on the side with a knife, then color over with black magic marker, wipe off with finger and get hair line graduation marks. When you are done, tilt upside down (to drain remaining epoxy) til the epoxy has set, and use over a few more times before you have to remove the cured epoxy lining. This is the best part - even though the sides are straight, the cured plug lining comes right out after loosening it and grabbing the edge with needlenose pliers and presto - clean as a whistle.

I used the same container over and over about 20- 30 times before it exothermed once and melted on me (the old kicked-with-a-heatgun trick to lower viscosity, de-air and better wetting - risky but worthwhile).
For those thinking that this is too difficult to keep the ratio, it really isn't if your good. Besides, a WEST System chemist told me that their epoxy is really optimal at a 4.5:1 ratio (5:1 being easier for marketing, and still well within optimal cure window), so if I err on the side of over-hardening I'm still in the ballpark.

Now THAT saves epoxy!

[N. Scheuer]

Had a friend once that built sailplane kits, using mainly epoxy/fiberglass structures. He had ONE type of small container and ONE type of large container.

He also had a light wood board scribed at the critical places, having used a ruler to scale off 1:5, with a correction for either a pair of the smaller cups, or a pair of the larger cups, which were not 1:5 in weight, of course.

He would merely balace the board agross a large-dia nail, like a 10-penney.

This way he could mix any quantity of resin by adding catalyst to the resin untill the balance tipped.

Moby Nick

[tealsmith1]

I bought a box of small dixie cups. Take one cup, cut in down on the bandsaw to the size I need. Then, fill it once with hardener and twice with resin. (making sure to scrape it clean between measurings.) When dried they help me start the next day's fire in the woodstove.

[Cedarhill Boatworks]

Where on earth do buy dixie cups that have to be cut with a bandsaw?

[Dan Lindberg]

For my usual small batches, I use syringes, generally mixing by the ml, up to 75 ml batches. However, on the odd occasion I have mixed op a batch by the drop, 2 to 1 for either MAS or System 3, and it's worked fine.

BTW, the stops inside the pumps are not a big deal, and can/could be easily changed to achieve a different ratio.

A MAS rep once told me that they were just restaurant condiment pumps and not very precise.

Dan

[imported_Sandman]

I screen print with Epoxy inks, so mix small batches most of the time, using dixi cups and a sliding weight scale. The inks I use mix to a 7% catalist ratio for one brand, both air and heat cure, although I sometimes mix the heat cure to as much as 20%. The other brand mixes at 20%; it's an air cure ink. Most of the time the weight of the cup is subtracted out of the equation, but not always. I've never had an ink mixing related failure in the 15 years I've been using it. This thread brings up a question I'd like to ask Chemist....Is the chemical make-up in epoxy inks the same, or similar to the epoxies used as glues? Thanks for the interesting topic, guys, and thanks to anyone who would answer my question.

[On Vacation]

Originally posted by Cedarhill Boatworks:
Where on earth do buy dixie cups that have to be cut with a bandsaw?It makes for a clean cut. Most of them come in 10 or 12 oz.

[ 03-14-2003, 07:53 PM: Message edited by: Oyster ]

[Nicholas Carey]

Get an Ohaus triple beam lab balance (mechanical) and measure by weight. You should be able to pick up a used balance on eBay for less than $50.00.

Lab balances are highly accurate -- more than you need. A lot of them are fairly high capacity, too (about 5 pounds or so). And some of them have tare beams that let you do the following:

</font> Put your container on the balance and zero the balance.</font> Measure your resin (50g of West resin). Zero the balance again.[*}Measure your hardener (10g of West hardener).</font> You're done&mdash;mix it up.</font>The Ohaus 2610 seems to be popular on eBay.

Or you could spring for an epoxy pump, but they run $200+ or so.

A little googling brought this up:

http://www.bertram31.com/proj/tips/mini-pump.htm

A homebrewed pump system using syringes and one hole stoppers. Check it out.

[Walcheren]

I have read all 20 responses. Nobody mentions the little measuring cups, 30ml,(and graded in ml. as well as drachms as well as teaspoons) that are used in the pharmacy and at home for measuring medications. I get a roll of them and either mix my epoxy, 2 to 1 in the cup or use 1/2 measure of hardener and a whole one of resin and mix it in a small plasic ,one serving, chocolate pudding containers. I do not use much epoxy, just at times to fix something or fill holes. Then I make a small, e.g. a 15ml mixture with sawdust and the job gets done. Hope this helps.

[NormMessinger]

System Three cautions about the accuracy of the first ounce in some paper graduated cups because of the accuracy with which the bottoms are rolled in.

[JimConlin]

A suggested variation on N. Carey's method:

Put your cup on the scale and zero it.
Measure the hardener first, an amount that is approx 1/6 the amount of mixed resin you want. If you're a bit over, no matter.
Note the weight of the hardener measured.
Zero the scale.
Measure the resin, 5x whatever the measure of the hardener was.

This method has the benefit of minimizing the relative difference between the masures of the resin and hardener.

When measuring cups of gooey materials, it's nice not to assume that you'll be able to scrape all of the goo from one cup into another.

[davef]

I have a small, relatively inexpensive digital scale which makes this an easy job. Tare out the bucket and do everything by weight. I would agree that with gooey substances, measuring the amount is less of a problem than ensuring you actually got it into the pot! The digital scale makes this easy.

good luck

[Dave Carnell]

40 years in chemical industry R&D impressed on my mind the basic inaccuracy of those ketchup pumps. The triple beam lab. balance weighs to about 0.05g. I accurately weigh batches as small as 1.5g for small gluing jobs. I keep the resin and hardener in detergent bottles for convenient dispensing.

[Bill Perkins]

All this points out the convenience of 1 to 1 mixes for mini batches . They allow one to operate at the opposite end of the precision scale .It can be as simple as drawing adjacent circles on the mixing surface with a compass ; pouring a puddle of A and a puddle of B ; then mixing . The viscosities are similar enough and the mix ratio forgiving enough for this to produce what seems to be a full strength mix .I've got a couple of gallons of T88 I'm going to be using soon and I intend to draw up a few sheets of paper with pairs of concentric circles of various radii , proportioned so the annulus is the same area as the center circle for a more compact pour and mix . I'll photocopy these onto the plastic transparencies that are widely available and keep them on hand for minimixes .

[NormMessinger]

And, all the Mill Landin' rigs for measuring goope just proves that it aint that critical. ...what ever trips your scale, er, floats your boat, eh.

[paul oman]

Hello I am in the epoxy business and mix up all kinds of "junk"

Most 'insiders' mix by weight. Just needs a good scale. Get mix ratio by weight by measuring out by volume ratio and then weighing how much A and how much B you have.

regards

paul oman
www.epoxyproducts.com/marine.html (http://www.epoxyproducts.com/marine.html)

[G. Schollmeier]

Mixing by weight is the weigh to go. :D
You can get a digital scale on ebay that will work for any size batch that one person would want to work with, and it won’t brake the bank.

TIP: Cover your scale with a piece of clear plastic film, an it will stay nice and clean.

Gary :D

[ 03-15-2003, 06:38 PM: Message edited by: G. Schollmeier ]

[scepticus]

Maybe I'm naive here... why not just use continue to use 3 cups as before, but fill them all only a fraction of the way. If you want a 1/4 batch, fill each cup ~1/4. Sure you waste a cup. Big deal. you don't care if it's exactly 1/4, just that they are all the same.

[Bob Cleek]

Sheesh, I though I'd get some solutions to the same problem I've had in here and it just gets worse! LOL First off, if you go for the Ohaus triple balance beam scale, make sure you aren't already under surveilance by your local narcs. The Ohaus triple beam is considered "indicia of dealing" in these parts! LOL The dope dealers use nothing else to measure their stuff. If you are caught with the "goods," you MIGHT be able to convince the federales it was for "personal use," but with the scales, you are dead meat on a dealing beef... Just a little advice from a former dope lawyer! LOL

Now, as for measuring googe in small batches, I do use the ketchup plungers for big stuff, but the problem is I have the gallon cans with the big plungers (it's LOTS cheaper by the gallon.) so I'm always using "half squirts." For smaller, really small batches, I use a spot the size of a four-bit piece for the resin and a spot the size of a dime for the hardner and mix 'em up on a hunk of tinfoil. For one to one ratios, like Smith's stuff, it's lots easier than anybody's suggested yet. You take a straight sided container, like, say, an empty tin can. (Forget dixie cups, and stuff you've got to BUY, for Pete's sake!) Then you take a popsicle stick (you DO save all your popsicle sticks, don't you?... if not, any old stick will work.) and you figure how deep you want the stuff you are mixing in the can. You make a mark on the stick with a pencil or whatever at that point. Then, for 50-50 ratios, you just make another mark half way between the end of the stick and your first mark. For 4:1, mark 1/5 up and so on... then you stick the stick inside the can and fill the can with the googe up to the appropriate line on the stick. Then you stir the stuff with the stick. When you are finished, you throw the whole mixing "system" in the garbage can and it costs you absolutely nothing. Works for me. Fact is, I've often just "eyeballed" WEST epoxy and it's never failed to kick off for me... sometimes takes longer, but... who's counting. I wouldn't advise that for really fine work like laminating hulls and so on, but for just stickin' stuff, close is good enough for government work.

[NormMessinger]

"...close is good enough for government work."

Well, now, I don't know about that but for epoxy work, for sure. Just how accurate does the manufactures of the goop say we gotta be? Plus or minus 10%, 15, 20.

Here's the balance I made and used when I built the Long EZ.

http://www.imagestation.com/picture/sraid55/p4268925c43504c497b422259502e026e/fc7d4785.jpg

The ratio for the epoxy used was 43/100 if I remember correctly. That determines the distance from the fulcrum to the center of cups. Place the empty cups in place and move the weights (a rock from the hanger floor works) until the scale balances. Pour in the desired amount of resin, then pour in hardner to rebalance, combine and mix. At least once a day let some epoxy harden in the bottom of a cup. Scratch it next day. If you get a good white scratch the mix ratio is good. There is nearly 1000 hours and 19 years on the airframe and no deterioration.

But for boats the katchup pumps are just fine but go ahead and make it complicated if you'll feel better. tongue.gif

[CK 17]

Norm,

Is that a long-eazie?
Joe Schena

[NormMessinger]

Um, well yes, I guess. I've heard them call pickle forks but never long-eazie. Rutan spells it long EZ. The smaller earlier version is the veri-eze. (Sheesh, and I accuse Donn of being snooty about spelling.)

Ya wanna go for a ride?

Best.

--Norm

[ 03-18-2003, 07:36 PM: Message edited by: NormMessinger ]

[Charlie J]

I've been using marks on a stick for years- ever since Meade Gougeon showed me how to do it at an EYA meeting in St Petersburg back in the late 70's. I use it all the time, both with MAS and it's 2-1 mix; and WEST with it's 5-1.

The containers I use are the inside cup from a spray paint cap. I band saw the outer part off and use the tiny straight sided cup inside. I have mixed (and quite often) 5/16s of resin and 1/16th of hardener, for a total amount of about a teaspoon full. Been doing it since, as I said, the late 1970s with absolutely no problems.

[CK 17]

Norm,

I knew what I wanted to say, I just forgot how it was spelled.

I wanted to build airplanes before boats. Then I decided that if something was going to go wrong with my workmanship it should happen at 6 knots, not 160 knots--so I switched to boats &lt;G&gt;

Afterall, what can possibly go wrong at 6 knots!!

Joe Schena

[ 03-18-2003, 09:46 PM: Message edited by: joe schena ]

[NormMessinger]

Right. It's a lot easier to learn to swim than to fly. Anyway, you know the definition of an airplane: It's a hole in the sky into which one blows money.