I've made a few molds using Amazing Mold Rubber, and cast a few parts from each using RC-3 and Alumilite White. What are the best ways to extend the life of these molds? If I do nothing at all but use them, approximately how many castings do you think I might get before the quality begins to go downhill? The details aren't intricate - for instance, one is a cabinet corner with a surface like pebble-grain vinyl, another is an old vintage radio-style knob - that's about as fancy as it gets. If I take steps to prolong the life of the mold, approximately how much more life can I expect to get from one?
For each mold, I don't expect to ever cast more than, say, 40 or 50 parts, if that many. At that rate of use, am I worrying about nothing?
The reason I ask, a couple of these I made from original parts that would be difficult to obtain again. For those, I've made or plan to make at least two molds.
If you are going to have trouble getting the original parts again then I'd make a good casting and keep that as a master in case you need to make a new mould in the future. It might not be quite as good as you would be making a copy of a copy but if you always use the same copy to make future moulds the quality shouldn't get any worse.
There is a "silicone oil" that is supposed to extend the life of a mold but I believe 40 or 50 parts is about the life of a mold anyway. Adrian is right - cast a good copy to keep as a master and if you ever need to make more castings than the original mold gives you then make a second one with the new master. On the new master, you could also "deepen" the details a little bit wherever possible (just deepen existing lines a bit) and then you'll have crisper lines in the mold which will keep the new copies looking just as good as the new master.
With Amazing Mold Rubber your going to get fewer than aprox. 40 resin pulls from the mold. HS 2-3 and Plat 55 will afford you somewhere between 50 to 200 resin pulls.....all of this depending on the type of part and mold along with the intricacy,detail, size of the part and how well the mold is cared for. It also depends on how often you are pouring, how hot your mold gets and if they are allowed to cool between pours.
Using a mold release before pouring can double the life of your mold. As Notoes mentioned ,there is Silicone Oil that Alumilite sells. Apply some oil to the mold before storing it. This will rejuvenate or restore some of the depleted silicone oil the casting resins removed from the silicone mold.
As Adrian pointed out, always make sure that you have a master copy. Either the very first resin pour that is without issues or the master/buck piece(s)