Dan, as already mentioned, for the faster projection papers you are using I would start with something like a frosted 7.5 watt or 15 watt bulb. You can always play around with the height that the bulb is from the paper to achieve an exposure suitable to allow any manipulation that may be required. I would recommend a frosted bulb because it should give more even illumination then a clear bulb. If these wattage ratings are giving you too long an exposure at a convenient lamp distance then step up to 25, 40, etc.
Originally Posted by DanielStone