Quote Originally Posted by Robbedoes View Post
...at the distance of 10 cm from a fluorescent bulb exposing for 1 minute each side of the spiral, mantaining it on the tank full of pure distilled water...

Each side: bottom and top side?

Mantaining it on the tank: how to expose it then? A transparent tank?
Yes, the spiral must remain below the water level in the tank.
After 1 minute you flip the spiral and expose the other "side".

The light will reach the emulsion sufficiently enough to expose the frames.
Occasionally you can take the spiral in your hand and expose not the side but the film itself such that the light is perpendicular to the film in the spiral.
But take care of not let the film go dry (that is the goal of mantaining it in the water).

I've found that taking the film out of the spiral is way too risky because at this point the emulsion is very soft and no hardener can cope with this.

Although I've not tried, putting the spiral in a transparent tank or container could do the trick.

How are the results you're achieving?