Step 1: Make Exposure Mask

Print a pcb picture on a transparent film. Print two identical copies of the picture.

Put them over, align well and tape together. The transparencies must be negative.

All transparent areas are final copper areas. All black areas are etching away.

You get best resul when print picture so that ink side is against to the pcb's copper (see the picture).

Sometimes you need to print a mirrored image. Usually it means that if the copper side is bottom, print normally picture and if the copper side is on top, print the mirrored picture.

Step 2: Clean Up Pcb.

If there is grease on the surface of the PCB, clean it with a solvent.

All alcohol based are good choice, example isopropanol.

Next remove all oxide using steel wool.

Now surface should be clean and polished.

Step 3: Film Over the Plate

When using a Dry Film, use only light that does not contain UV radiation..

Remove protective film. My experience shows that the dental tool is the best for this.

Sharp needle works as well.

Put the Dry Film top of pcb. Remove all air bubbles.

Heat up a moument with a hair dryer or heat gun.

Now the dry film adheres to the pcb. If the film not stick to pcb , heat is too low or time too short.

Step 4: Exposure

You can buy an exposure device or make your own. One simple option is to use a glass sheet and a lamp above it. The only condition is that the lamp emits ultraviolet light.

The exposure time is usually few seconds to few minutes, the time depends on the lamp power and distance to the pcb. My own exposure device is made from an old scanner and a face solarium.

It works well, the exposure time is only 15 seconds.

And that exposure.......
Put exposure mask against to pcb and switch light on. When the time is full switch light off. If everything went as it should, the same image as the mask appears on the surface of the plate (as in the picture).

WARNING!!!! uv light is dangerous for the eyes, use suitable goggles (block uv), do not stare at light or cover the exposure unit.