Thanks jeanna, I am impressed to see how little the MgSO4 solution attacked the magnesium ribbon compared to the Salt solution !!
That's a very important point !!
What is your recipe to prepare the MgSO4 solution ? Where you bought it, what quantity in water ? ... Edit: Ok I found that MgSo4 is just Epson Salt 

Even the copper seems not corroded at all !

I want to try to make graphite thin film ... powdering graphite then put that on glue tape, to save on the graphite volume used ...
I read somewhere that they use wax and/or clay mixed with the graphite to make the pencils. I'll try to see what results I can have to make a graphite thin film in my kitchen 

I'll try also copper as you suggested 

@ Stefanafreter:

You can get cheap powdered graphite designed to be used as a lock dry lubricant.  It comes in a small toothpaste type tube and would be easy to use for your tape idea.
Any auto parts place should have some, along with some hardware stores, etc.

Bill

Nice one Jeanna.

Hi guys impressive batteries. Anyone knows where to find magnesium from trash?
Cookware maybe?
Thanks

Yep, thanks Pirate, I found Graphite and Lithium grease for less than 10 USD a pot in the "Home Depot" ... going to try them as electrodes as soon as they are dried up a bit.
I also put some graphite grease on a piece of pvc pipe, and added some graphite powder to thicken and densify the layer (can buy from artist drawing shop, 10 USD for 150g pot).
I'll keep you informed asap.

Edit: Grease is a strong insulator, be sure to add a lot of graphite powder to the grease until it becomes electrically conductive !!
I put a layer of plastic net underneath that I fill with the mix, to get an even layer on all the surface.

I also got some candle wax to try to mix it warm with graphite powder, because when cooled it could form a stronger and thicker layer, and it could be molded in any form ...

I think magnesium powder is very hard to find, because it is highly reactive to air and water ... but it's used in fireworks, mixed with aluminum powder to.
I'll first use magnesium ribbon with a file to make small quantities of powder for testing.