Request: Conductive ink formulas for through-hole activation

[technobabble]

I've been making conductive ink out of acrylic ink and graphite for a little while now.  It seems to work okay but it's shelf life is horrible.  It clumps on the bottom and becomes unusable even if I mix it it every day. 

The think and tinker website sells 50g of conductive ink for 110 USD but before I pick up something that expensive, I was wondering if any of you guys had a formula that might work a little better. 

Right now I'm making new batches every run and throwing it away after.  It's cheap enough to do so, but any advice would be appreciated.

[Rerouter]

never done this myself, but perhaps a binding agent, simply because graphite isnt the simplest thing to bind into other chemicals,

the simple properties apply, very poor with water or organic based chemicals, though thats where acrylic comes in i suppose, just make sure your ink hasnt been diluted with water

[technobabble]

I've read that as the acrylic dries down the suspended graphite presses together and forms a conductive ink.  The ink in the vias is cured with an iron to make sure it's as dry as it can possibly be. 

In the end my through holes have a resistance of about 30 ohms.  I'm wondering if professional inks give less resistance than that.

[mikeselectricstuff]

These people make a new low-cost carbon & water based conductive ink that may be worth trying
http://bareconductive.com/

[HLA-27b]

I too read somewhere that graphite is notoriously difficult to mix with anything due to its high surface area. Hours of mixing time was mentioned. It might be worthwhile to mix graphite with a thin solvent first, something like ether or acetone, and then adding this to your binder.

[westfw]

I've made "conductive pyrogen" ignitors with lubricant-grade graphite and white glue ("Elmers"), and it holds up OK, but I wouldn't want to squeegee it through .6mm holes.  It's not clear whether larger or smaller graphite particles yield a more conductive result.  Less binder is probably better.  It almost sounds like your acrylic is reacting with the carbon, which seems vaguely chemically possible.  Try other binders.

There is also conductive lampblack.  Messy as hell.

You might experiment with the carbon rods from C/Zn batteries.

Commercial inks tend to contain silver or palladium.  Expensive!

[technobabble]

I'll try a couple other inks, they're pretty cheap to experiment with. 
Would any of you have any interest in experimenting with the real stuff if I purchased a bottle?  It looks to be about 20USD per 10grams.  I doubt I would ever user use all of it, so if anyone is interested in trying it out but doesn't want to spend 110USD on the experiment, let me know.