This is the set up i have used for a number of years. The propagator is set up, covered with insulating silver bubbly film cut to the shape of the propagator cover. Holes are cut in the film to allow LED lights to be directed into the propagator. I have covered the development of these in previous articles. The silvered bubble film provides two functions, insulate the propagator but primarily to trap and bounce the light around inside to maximise the illumination of the seeds to help germination. Using the LED lights and silver film means that the LED lights can be used consuming less power for the same amount of light output compared to a standard grow lamp which has to be kept a safe distance from the seedlings to avoid heat damage.
This photograph shows the progress of the Begonia seedlings so far. These were sown on the 10th January 2018 and both trays have shown good progress.
The first germination was seen around the 18th January and since then the seedlings have developed well.