I have been looking into PCB etching and it seems as though there is no affordable way of adding a decent solder mask without ordering UV curable soldermask ink from ebay (which I would like to avoid). I don't think I need one since the smallest part I use is an 805 SMT resistor, correct me if I am wrong about this.
I am fine with bare copper showing on the board if oxidation is not a problem. How long does it take for a copper PCB to oxidize to a point that it is unusable after the soldering has already been done? I am sure this varies with humidity but ballpark it for me. For reference, I live in Washington State which is not as humid as a tropical climate, but it rains/snows often.
If you are that concerned, why not paint the tracks with nail varnish?
define "unusable". If you mean that the traces will still be viable conductors, don't worry. If you mean still solderable, you still shouldn't worry. a little steel wool and they should be fine.
Rather than steel wool - which will conduct if you leave bits behind - try a typewriter rubber (that's an eraser if you live in the USA otherwise you might not get what you want :D)
Not sure if this is the same thing that CrossRoads posted but I have used Tinning Salts for many years:-
http://uk.rs-online.com/web/p/products/0551514/
Given the reasonably priced PCB services out there, I cannot imagine entertaining the thought of ever making my own again! Washington State is OSH Park's backyard, you're aware of them?
Mega do a dry film solder resist applied by a laminator.
Ive also used tinning salts with good results although you have to solder within a few months.
If you are storing boards for a period of time , leave them as copper and clean before use.