Sorry to say, but no. Water and Vaseline have no effect on the hardening rate. It's a chemical reaction between the two parts (resin and hardener) of the epoxy putty. Water and Vaseline are useful as lubricants to stop
GS sticking to sculpting tools, but that's about it.
What
does affect hardening rate is temperature. As it's a chemical reaction, it's slowed by cold and accelerated by heat. All the time, hobbyists and sculptors quickly harden (or 'cure') parts and figures they've modelled by putting them under a desklamp or exposing them to some other relatively gentle source of heat. (I say
relatively: You don't want to burn your models, but it'll take more than breathing on them to hurry things along!) On the other hand, freshly-mixed putty can be stored in a freezer for 1-3 days to prevent it curing.
There are other sources of green stuff to buy from, too. It's not a Games Workshop product, but bought in from Polymeric Systems Inc. in the US, where it's official name is Kneadatite Blue/Yellow. It's repackaged, relabelled, and given a terrific markup price. Here in the
UK GW sells 20g (0.7oz) for £6.15, while other hobby suppliers sell it for, at most, £10-12 for 100g (3.5oz). 100g of green stuff from
GW would cost just over £30.
Other hobby suppliers usually sell it in PSI's own packaging - hence the 100g quantities - as a 36 inch coiled strip in a box or as two cylindrical bars in a tube. The tube is quite good as the two parts are wrapped seperately and prevented from touching. That's a problem with the strip form, as the two parts meet in the middle and cause unwanted curing and other problems. Still, that can be helped by cutting out a millimetre or two from the middle of the strip, separating the two parts. 100g or 36" can seem like a daunting amount of green stuff to use or keep too, but that's where the handy freezer tip comes in again. If you don't use it up very quickly, you can store it there, or in the fridge, to keep it fresh.
In use, green stuff has a kind of elastic consistency like chewing gum or sticky tack. The non-crumbly texture is what makes it appealing to many mini converters and sculptors (besides it's ability to survive the vulcanisation process for spincast moulds) but it also has a bit of 'memory', a sort of springiness that makes it 'spring back' or 'spring out'. That doesn't mean your modelling will snap back into a ball shape, but it can make very fine details and sharp edges difficult to maintain.
The usual method of mixing epoxy putty is equal amounts of each part, though recently PSI started recommending a mix of 1.5 parts yellow to 1 part blue for general modelling. This has the effect of making the green mix softer and easier to push around; a bit lighter in colour, for seeing detail more easily; extending the amount of time you have to work with it before it becomes too stiff and tough; and reducing that springy memory. It's a pretty good idea. Although if you want a stiffer mix that cures a bit sooner, more blue can always be mixed in.
In my experience epoxy putties always prefer to stick to sculpting tools than to anything else (except fingers). So lubrication. Water and Vaseline are two of the most common methods, as mentioned. I prefer water, myself, dabbing the sculpting tool on a moist sponge rather than dunking it in a jar of water. Too much water running over the surface of the putty can obscure details, and run round the back to prevent it sticking to what you want it to stick to. Others swear by Vaseline, and it seems to work well for them, but you need to wash it off after the putty cures, or between putty layers. The third category overlaps the other two a little: Bodily fluids. Specifically spit and forehead/T-zone grease.
On that note, green stuff is not poisonous. The sculptor who first started using it years ago, Tom Meier, once quoted that the most toxic ingredients in it are the food colourings that make it blue and yellow. But like all epoxy products, it can cause sensitisation which leads to allergy-like symptoms. When and how this happens seems to vary - I've used several types of epoxy putty with my bare hands, for years, and fortunately haven't had any reactions yet. Nevertheless, epoxy putty manufacturers put, or will soon be required to put, warnings on their products to use gloves. Whether you want to is up to you, but my point (finally) is that if gloves to protect your hands are recommended, is it a great idea to rub a putty-layered tool across your head, or lick it?
As you're in the US, ConCon, I feel almost obliged to point out
Troll Forged Miniatures as a green stuff retailer. But it's your choice where you buy.
And that page brings me on to other putties. Procreate, featured there, is also a pretty good putty for beginners. It's light coloured, easily shaped, and has very little 'memory' (although, green stuff is the only putty that does have that quality) though it is just a
wee bit less elastic than green stuff.
Milliput is a clay-like putty. It has a kind of crumbliness and soft feel that's a bit like real clay. It also dissolves slightly with water, like real clay. This makes it easy to lubricate and smooth with water, though in a different way to water-repellent green stuff; but again, too much water isn't recommended! That can start to create a bit of a mess, although as Tjomball mentioned, the resulting slippery 'mud' can be useful in certain circumstances too, for brushing over pinholes and tiny gaps on a mini. Milliput also cures rock-hard, compared to the slightly rubbery final state of green stuff and procreate, which makes milliput quite good for scraping, sanding, carving etc. It's also quite strong.
Although, while I don't want to put you off it, I'd say the stickiness, crumbliness, and particular qualities of milliput are more difficult to get to grips with than the other two putties. Not to mention that as a
UK product, it's got a few import markups in US stores. If you see it, and want to give it a go, go right ahead. I like it and use it a lot, myself. But there are,
AFAIK, similar products over your way, like Rezolin A+B or Kneadatite A/B (another PSI product). Or others like Apoxie Sculpt and Magic Sculp. Those two are also claylike putties, but developed specifically for sculpting and modelling. They're even softer and a bit more fragile when mixed, for the kind of tiny quantities and details needed for most 28mm scale modelling, but they soon firm up, and they've got finer textures and are less water-soluble. (For
UK readers, apoxie sculpt and magic sculp are available here too, but I recommend you also google the Restoration Supplies shop for homegrown Cold Clay and aSculpt)
Mixing some elastic putty, especially green stuff, into a clay-like putty can combine their best qualities and reduce their worst, 'loosening' green stuff while binding and reducing claylike crumbliness, and producing a pretty pleasant modelling medium for wargaming minis and scales. I know and have read of a lot of hobbyists and pro sculptors who do this. I do it myself, most of the time! Maybe you don't want to go so far at the moment, especially if you just want to fill a gap or two, but keep it in mind if your conversion ambitions begin to grow.
Take a look at the forum in my sig, too, and maybe peek at the 'tools and materials' board. There are a few sticky topics there with links to articles on what different putties are like, and links to where you can buy them, not to mention discussion on the rest of the board. The US list isn't as extensive as the
UK one, but still has a few decent suggestions, and anyone's free and welcome to point out any additions I can make.
