Hello everybody. My name is Stephan and I started to try my first Daguerreotypes since beginning of this year. Polishing and fumigation (first magenta) work well. I took each photo in the full sun and the image is of a black and white sign with a bit of background around it. EV was 14.5 and I used 50 sec exposure time at f.5.6. I also made sure that each test is done under the same conditions in terms of outside temperature (around 30 celcius), lighting and time of the day.
I seem to have a problem with developing the picture though. Every time I put a plate under the rubylith mask the brightest parts of the image (it is negative) appear very crisp after only 30 seconds. I red in other descriptions that it should take up to 15 minutes until anything becomes visible. I am also aware that looking through the Rubylith enhances the crispiness and I know that I am supposed to leave the plate under the Rubylith for at least 1.5 hours which I did. But right after about 2-3 minutes the image on the plate starts to fog and disappear again. Then after an hour there is only a very faint image left (which is positive now though).
First I thought there is white light getting into the box somehow. I taped the box everywhere to make sure this is not the case and it made no difference. I also installed a fan to avoid fogging due to the heat.
I am living in New Zealand and the sun is stinging in summertime. The UV is about 40% stronger than in other countries and I am starting to wonder if this is causing the problem. I am also suspecting that the heat is the reason for the fogging.
It would be great if anybody could help with a bit of advice. Thank you so much in advance.