Photoresist newbie here
So I purchase some dry film photoresist its unbranded and the website I bought it from doesn't have any specific instructions of developing.
However I found a instructable at this link
https://www.instructables.com/id/Dry-Film-Photopolymer-for-making-circuit-boards/So I went thu the usual steps of first printing a negative of my artwork on tracing paper with a laser printer. One sheet was not providing me high contrast So I printed on 2 tracing paper sheets and overlapped them.
The I stuck the photoresist film on the copper side of the pcb and laminated it with a hot iron
Then I kept my tracing paper over this with the printed side closest to the photoresist film.
I exposed it in bright sunlight for 10min.
The I tried developing it in 1% sodium carbonate solution. (5gm of soda ash in 500ml of distilled water) but after 3 min I washed the pcb in water and say than only a few small spots had exposed copper. I did developing for another 3min and just a little most copper got uncovered.
I have attached the picture of the pcb.
What did I do wrong here
1. Did I overexpose the film, so its difficult to develop now.
2. Is my developing solution too mild and do I need to do 3% concentration of sodium carbonate. Because I used distilled water at around 30 deg.