When the weather is warm I don't get too nervous about shooting cold molds and injectors but as the temp drop I change things just slightly.
First, I like to have some heat in the mold so I wrap it in a single layer black plastic [3 mil] and set the mold in the sunshine for about a half hour. This really gets the chill out of the metal and I don't get any sweating. Second I'll run a dummy shot into the mold and let it sit for a minute before popping it open and emptying.
Using my thermometer this morning I found the mold I needed to shoot for a split color number to be 38 degrees. We have some nice sun today so I did the wrap number and laid the mold out on an already warm surface and let the sun do its thing. while I whipped up the plastic. I had already laid the tail sections back in the mold so I didn't bother with the warm-up shot when I had everything ready. I shot as per usual and held some light pressure on the injector for a few seconds and things worked out just fine.
I know some talk here expressed some concern when warming molds on hot plates and possible warping of the molds, so this might be an alternative you may want to check out if you have any doubts about the hot plate route. I've been doing this for as long as its been getting colder at nights up here. I'll note that I am shooting the soft formula of Caney Crystal Clear and I do heat the second color about 10 degrees over the 350 so I add stabilizer to the second color. Since starting the practice of getting some slow natural heat in the molds before I do any two color shots I have been getting no bad joints in the welds.
