Peel it back carefully. Exposing your board For best results, use M.G. Chemicals cat. Artwork should be place printed side down to prevent light leakage through the side of the transparency, and should have been produced by a 600 dpi printer or better. Use a 5 minute exposure time at a distance of 5 inches. The development process removes any photoresist which was exposed through the film positive to ultraviolet light.
Developer contains sodium hydroxide and is highly corrosive.
Avoid contact with eyes and skin. Flush thoroughly with water for 15 minutes if it is splashed in eyes or on the skin. In a plastic tray. Immerse the board copper side up into the developer, and you will quickly see an image appear while lightly brushing the resist with a foam brush. This should be completed within one to two minutes.