Protecting diy pcb boards....

After etching, any suggestions on protecting the copper tracks from oxidizing? (Since these boards don't have a silkscreen)

Varnish? Lacquer? Glue?

I use:

You can also spay a clear lacquer after you solder everything. Also look at conformal coating. There is a heat transferable solder mask sometimes offered on eBay.

Oh nice! Better than covering the entire board, thanks!

I guess an even spread/layer of solder paste would do in an emergency ..

There is also a rub-on silver plating (the rub-on Silver coating "Cool-Amp" - Thanks) that I used to use. A little of that powder on a wet cloth plated the board in less than a minute. But it did tarnish a bit after a few months. But card-edge connectors plated with it worked well for years. I'll try to find the name of That Stuff.

I use the rub-on Silver coating "Cool-Amp" in combination with a clear coat lacquer sprayed "before" soldering. The Lacquer melts away while soldering and you end up with a protected board that won't look ugly due to tarnish. Personal experience is that it takes a long time for the Cool-Amp to actually show tarnish even when not painted over with clear coat.

The product for silver plating copper may seem expensive, but I have had mine for nearly 10 years and have only used about 10% of what is on the jar.