Use Vaseline as a resist and a bath of salt and vinegar to etch away the copper from copper fabric to make circuits and sensors.

More pictures on Flickr:

Inspired by instructions from Rehmi Post and Kit Waal.

Also see Sew-through Soft Circuits post by Meredith Scheff on The Steampunk Workshop:

Tested mix:
*100ml vinegar
*7ml salt

Insert piece of copper fabric. With resist applied to the areas taht you do not wish to etch away the copper from. See bellow list of resist media. For copper fabric we have been using pure copper polyester tefta fabric sold by LessEMF.
It takes up to 12 hours for the first piece of fabric to etch, but after that the following pieces take roughly 2 hours.

In the above examples the resisting medium (Vaseline) was only applied to one side of the fabric. Even though the Vaseline penetrates the fabric it does not protect the reverse side from etching. As can be seen in the following image.

Resist on both sides
If you want to preserve more of the copper you can apply Vaseline (or another medium of resist) to both sides of the copper fabric. The following photos show an example of this.

Images taken with USB microscope:

Mediums tested for resist against etching:
*Vaseline – great! (and you can iron off Vaseline into a paper towel)
*paper stickers – good, but they leave stickiness behind
*masking tape – good, but takes off some of the copper
*drawing with wax from candle – good, but have to scrape or iron off wax afterward
*duct tape – okay, but takes off a lot of copper with it
*stickytape – okay, but takes off a lot of copper with it
*hot glue – okay, but takes off a lot of copper with it
*fusible interfacing – works, but hard to get off afterward
*melted candle wax – doesn’t work great