PCB etching

Introduction

Now that we have our wires plotted on the PCB, we need to remove the areas not covered by marker's paint. This process is called "PCB etching". There are many ways of doing it, I will use the one that is simple, safe for in-home implementation, and reliable. Here is an example:

The process

We will use salt, citric acid and hydrogen peroxide. First two ingredients can be purchased in a food store, the third one is available in a pharmacy (a 3% solution is just what we need). Weigth components, add the solution to a shallow vessel (pod, plate...) and submerge your PCB it. Keep mixing the solution gently, until all excessive copper is gone. Wash and dry the PCB after it is done.

Here's a recipe for approximately 100ml of solution:
10-15 grams of table salt (sodium chloride)
10-15 grams of citric acid powder
100ml of 3% hydrogen peroxide (approximately 100 grams)