EPOXY - accurate and no waste when mixing small amounts by weight.

[Gearup]

Epoxy...Strong, expensive and somewhat wasteful or poorly mixed when prepared in small amounts. Here is a way to mix very small amounts of epoxy accurately and without wasting it in mixing cups, coating spatulas  or just mixing too much.

The scale is accurate to 0.01 grams. A single drop of water from a pipette is 0.05 grams. If a fan is on near the scale it will register the force of the air moving across it. Cool.

Note: The "epoxy" used in the pictures was carpenters glue for illustration. After you have weighed out the epoxy, you can add thickeners such as micro-balloons or colloidal silica before sealing the bag. A bit of experimentation is in order here.

Tools and materials.
micro scale - MAXUS Precision Pocket Scale 200g x 0.01g Available from Amazon 15 dollars!
small plastic craft ziplock bags - aprox 6x8 cm, dollar store
popsicle craft sticks -dollar store
small elastic bands - dollar store
one ounce plastic condiment container - comes with fries or from the dollar store
wax paper
epoxy - the two part example is G-2 by System Three. Mixing by weight ratio is used.
sharp knife

• Cut the bottom off the condiment container
• Make sure the ziplock bag is open then cut off the excess flap above the seal.
• Roll down the open rim of the plastic bag
• Push the bag through the open end of the plastic cup.
• Place the plastic cup with the bag opening facing up onto a small sheet of wax paper to protect the scale and zero the scale with the cup sitting on the scale (tare weight)
• Add the desired amount of resin and calculate the amount of hardener required using the observed weight of the resin in the bag. For Example: G2 is a ratio of 100 resin to 44 hardener by weight. Therefore 0.57 g of resin would need 0.25 gram of hardener. 

Calculation: 0.57g resin x .44 = 0.25g hardener.

• Re zero the scale and add the hardener.
• Remove the bag of epoxy mix. Don't squeeze the bag.
• Squeegee the mixture to the bottom of the bag then squeegee the air out of the top and seal the bag. Do not squeegee the mixture and trap it hard to the bottom to avoid bursting the bag at any time.
• Squeegee or massage the mixture until completely mixed for about 30 seconds or so.
• Squeegee the mixture away from one of the bottom corners.
• Place two sticks across the bag and secure them together with small rubber bands. They will act as the dispenser squeegee.
• Cut a small tip from the corner to dispense the epoxy.
• Use the sticks to squeegee the epoxy out from the corner.
• Only the plastic bag needs to be discarded. Everything else can be reused!

It takes way longer to read this article than to actually mix up the epoxy...

Fraser

[Gearup]

more pictures. Order is a bit screwed up ... Read the post below for the beginning.

[Boomerang]

Excellent "how to" presentation.

 Thank you Fraser

Gordon

[Gearup]

Epoxied a test piece with a "wing" butt joined to a "fuselage" to see how it was for strength.

The spruce "fuselage" section was held in a vice with the 1" wide x 8" long x 1/8" thick "wing" horizontal. It was marked in 1" increments from the root to 5 inches.

I suspended a 16.5 oz weight (467 gram) at the one inch mark and it was fine. I moved it outboard an inch at a time until it failed at five inches. That's 82.5 in/oz of torque  or about 0.58 nm. I was quite surprised by the strength and should hold the wings on with normal handling.