To make your own conductive glue, you will be taking an insulator (Liquid Tape rubber or DAP Contact Cement) and turning it into an electrical conductor. This is done by the addition of carbon graphite powder which is a conductor. As the binder (LT or DAP) sets up, the carbon crystal flakes stack on each other and intertwine to make the glue conductive. The result is a flexible conductive glue that will stick well to most things.
The glass circuit doodle in pic3 below, is used to illustrate some of the ways the different glues can be used. Click on the comment squares for details.
Since my first instructable on how to make conductive glue: http://www.instructables.com/id/EYA7OBKF3JESXBI/ I have been experimenting with various conductive materials. In the process, I have come up with a few new mixes using other binders that have somewhat different characteristics than the original conductive rubber glue.
Performix (tm) liquid tape, black-Available at Wal-Mart or http://www.thetapeworks.com/liquid-tape.htm
DAP "The Original" Contact Cement- available at Wal-Mart or most hardware stores.
Carbon Graphite, fine powder- Available in larger quantities at http://www.elementalscientific.net/
Available in smaller quantities at your local hardware store. It's called lubricating graphite and comes in small tubes or bottles. The brand I used is called AGS Extra Fine Graphite, but no doubt there are other brands that will also work.
Conductive thread-Available in small spools at http://members.shaw.ca/ubik/thread/order.html
Clear contact cement such as Welder Contact Adhesive or Goop- available at Wal-Mart and hardware stores
Tuloul solvent- available at hardware stores
WARNING- All of these mixes involve strong solvents that evaporate into the air quickly. Do this only in a VERY WELL VENTILATED room. The fumes can be harmful. Better yet, do it outside.
All of the mixes below are best mixed in small quantities and used immediately. I have tried storing them in airtight containers but all of them seem to harden up after just a few days. Mix them in a stainless steel or glass container. You can mix them in plastic cups, but you will have to do it fast as most of them will dissolve many plastics.
Glue mix #1 Conductive Glue Using Liquid Tape (LT)
This is the original formula that uses a mix of Liquid Tape and Graphite powder. It results in a flexible conductive rubber that actually shrinks as the solvents evaporate, thus tightening it around whatever it coats. It has the lowest resistance of any of the unfibered mixes (32 ohms per inch). For details on how I measured the resistance see the original instructable (link) on this glue. I find it best for gluing wire to wire, or wire to conductive thread or conductive fabric. It can also be used to make conductive foam (see step 4).
Mix the glue 1-1/2 Graphite to 1 Liquid Tape by volume. Mix it fast in small quantities and use it fast as it tends to evaporate and skin up rather quickly.
I usually use 1/4 teaspoon as my unit of volume.
Mix #2 Conductive Paint Using Liquid Tape
This is the same mix as above with the addition of extra solvent to make it the consistancy of thick paint. Because it is a thinner mix, it has a higher resistance (60 ohms per inch) than the conductive glue. It is useful for making conductive thread and conductive fabric (see step 6). It also sticks better to glass than the thicker glue above.
Mix the paint 1-1/2 Graphite to 1 Liquid Tape to 1 Tuloul by volume.
Mix #3 Conductive Ink Using Liquid Tape
I mainly use this ink for touch up if the glue lines get too sloppy or to re-coat close together joints. Because it is so thinned out, it can have a rather high resistance in the hundreds of ohms per inch. It can also be used to create thin film high value resistors and It may be useful for high voltage applications.
Mix the ink 1-1/2 Graphite to 1 Liquid Tape to 3 Tuloul by volume.
Mix #4 Conductive Glue Using Dap Contact Cement
It turns out that most contact cements will become conductive if you add graphite. Even Elmers rubber cement has very low resistance when mixed with graphite. It is however, a raw latex rubber and I do not trust its longevity as raw rubber tends to deteriorate with time.
The DAP Contact Cement is a more industrial strength rubber and it had the lowest resistance of any of the heavy duty contact cements that I tested. While Its resistance is higher (62 ohms per inch) than the Liquid Tape glue. Its biggest advantage is that it does not shrink as much as the LT glue. It is also much more flexible than anything else I tried. This makes it ideal for coating the surface of fabrics without making them curl, to create conductive fabrics, potentiometers, resistors, switches and sockets.
Mix the DAP Contact Cement glue 1-1/2 Graphite to 1 Dap.
Mix #5 Translucent Conductive Glue.
See pic 3B. While I have so far been unable to come up with a clear conductive glue, this is as close as I have gotten. In all of the glues I have been making, I have resisted adding metal powders, or graphite fibers to increase the conductivity, as this makes the glue much more brittle or stiffer. I am trying to keep all the glues flexible as this makes for more interesting possibilities in what can be made conductive. So instead of stiff fibers such as graphite fibers or metal wire, I added flexible conductive thread. And yes, I know, you could just run the thread and skip the glue, but this has interesting artistic possiblilites.
The translucent glue is simply conductive thread that has been unraveled and chopped up into 1/4 inch long pieces. It is then mixed with a clear contact cement such as Welders or Goop. With Welders Contact Cement, I obtained a conductivity as low as 12 ohms per inch.
Mix the translucent glue 1/4 teaspoon clear contact cement with 6 to 12 inches of unraveled and chopped up conductive thread.
Mix #7 Resistor Glue
Mix the resistor glue 1/2 Graphite to 1 Dap contact cement by volume
Less than 1/2 units of graphite can result in a very high resistance or even an insulator.