<p>invisible ink is also a viable option. milk works as invisible ink on white paper, and is probably more accessible - and when you hold it to the light, you can see your notes! you will never have to buy pens again.</p>
<p>invisible ink is also a viable option. milk works as invisible ink on white paper, and is probably more accessible - and when you hold it to the light, you can see your notes! you will never have to buy pens again.</p>