Brief: I use XTOL as a replenished developer so I always have 1 litre of working solution mixed and stored to the brim in a thick brown glass bottle. Now the weather is turning, the room where I develop the film is going to drop., in fact as I write this, my working solution is at 17°C Question: To bring the working solution up to 20°C I could ... Put the glass bottle into some warm water and wait for the temp of the developer to rise but this could take some time due to the thickness of the glass bottle Pour out the amount I need into a thin plastic jug and then place that into some warmer water and wait for the temp of the developer to rise. The developer is now open to the air so would this cause it to oxidise quickly and lose its strength. Use a temperature conversion chart and just adjust time according to current temp of developer Which option would be sufficient?