Experiments with snow pt1

After posting my challenge casualty the other day, I got some nice comments about the snow asking how I'd done it. It's been  a while since I've just sat down and had a play with different techniques, so here are some notes I made last year (fleshed out a bit). I'll do a part 2 sometime soon, onc eI've worked out how to take better photos of the snow!!

GW Snow effect

The GW winter effects pack looked fairly promising in the shop, but getting it home and trying to use it was... interesting. This stuff is, as far as I'm concerned, pretty naff if you want to create actual snow as it is basically white static grass. It can be useful for the odd bit of frost covered grass when applied over white glue or varnish; other than that... I wouldn't bother.

Interestingly (or not) their effects packs contain no instructions at all on how to use the stuff. I guess they just assume you'll use it in the same way as flock, but I ran some experiments with it anyway. I wanted to see  how this GW snow reacts with different mediums; in this case, white glue (WG), MIG acrylic resin (R) and GW 'Ardcote gloss varnish (V). The image is a little tricky to see some of the differences; zooming in does help a bit.



Going left to right we've got each medium either mixed (+), or used to stick the flock on (-> ). For example top left is a mixture of the Vallejo resin and the snow flock (R+F) and bottom left is a layer of resin painted onto the base, with some flock over the top (R->F).

As you can see, in all the cases where the flock is laid over the top of the sticky medium it's fairly transparent so you can see a difference between the colours underneath. Whichever medium is chosen, you get light, fluffy looking effect that looks fresh, but thin. If you're doing this, white glue is probably your best (and cheapest) bet. For deeper snow you could try painting the surface with a very very pale blue first to give it a deeper, colder feel.

Mixing the flock with the different mediums is where we start to get some more interesting effects. In each case I've not been overly careful on quantities, but I did learn that mixing a small batch and applying it, then mixing a little bit more works better than trying to do a larger batch in one go as it tends to become clumpy.

Gloss varnish and the resin seem to give very similar effects; I would imagine water effect would also give the same look. In each case, the snow is quite thick, but slightly shiny, as if it's slowly melting in the sun, or under foot. Mixing the snow effect with the pva glue gives a very matt, almost paper-ish looking snow, which is good for very dense, compacted snow, or using as a base for another snow effect.

In future articles I'll be covering some other effects, including crushed glass and baking soda

Learning to cast resin

While I'm on a roll resurrecting old tutorials, here's some notes from my ventures into casting. I'll go back and revisit this sometime in the future and flesh it out a bit more, but it may be of use to someone in it's current state.

There's a shed load of stuff you need, all of them pretty cheap to get hold of and useful. I kept having to do trips into town at the weekends to pick up something else :

- RTV rubber
- the fast cast resin
- plasticine
- wooden spatulas (either buy lots of cheap ice lollies from Asda and feel refreshed each time you make a mold or cast, or Tomps sell boxes of 100)
- syringes
- lots of lego blocks, preferably the 2x4 or longer, plus a large, thin base
- plastic party cups (50p for 100 from Asda)
- Vaseline.
- a cheap brush
- something to melt vaseline in, I've got a cheap curry bowl from Poundland
- some decent scales; the more accurate the better.
- lots of old sprues to make the pouring channels in the molds
- Talc

JB's casting tutorial in the Articles section of DakkaDakka.com is pretty good, with a few modifications as noted below. I think most of the variations are because I couldn't get hold of the molding putty he used in the UK without paying a fortune to import it. In the UK, the best place to get resin and the RTV rubber is http://www.tomps.com , they were quick to respond to my questions and are planning on putting together a beginner's pack sometime soon. Just don't be fooled into buying the casting manual they have... the useful bits are already on their website; the rest you really don't need.

1. Why the Vaseline?
A number of tutorials suggest putting a layer of olive oil on the first half of the mould. this may work if you're using putty that JB uses. This doesn't seem to stop the RTV rubber from sticking together though, so a thin layer of melted vaseline painted over the rubber (not the models!) will help you not to make a large blue rubber block. Painting over the models as well will obscure details, making the casting process pretty pointless. You can use a spray can of release agent, but Tomps didn't think it was necessary while I was learning as I'm unlikely to want the early molds to last too long.

2. Why the Talc?
The first test cast I did came out minus most of the smaller details. There were no visible air bubbles in the casts, it just didn't seem to have made it into all the corners so everything looked a little melty. A layer of talc on the two halves of the rubber before casting (with the excess shaken off of course) seems to help the resin flow into some more details; though it's still not 100% crisp, but this may have been to talc being missing in some placed.

3. Why the syringe?
Leaving gravity to do it all may work if you're only doing one or two large bits, but if you're trying to do smaller things like rifles with fiddly bits, you're going to need some pressure to get it flowing through the vents. Be careful not to push the syringe into the channels when injecting the resin though as you'll push the two halves apart and cause leakage/air bubbles.

4. where's the elastic bands mentioned in the Article?
The first time I tried casting, I did have elastic bands and card around the molds, but it didn't seem to be working very well. The molds were deforming and I was getting a lot of leakage and air bubbles. Luckily the two molds that I'd made, side by side, can be secured between lego blocks on the base. This allows nice even pressure across everything apart from the top. It's not stopped the flash from forming, but it's now significantly less than with the elastic band. I think I just need to put more bits of card in between the molds and the lego, to increase the pressure slightly.

5. Think about the placement of your pieces in the mold
As the title says... think carefully and make sure there aren't any bits that are going to trap air.you are injecting the resin in, so you'll need somewhere for the air to come out. I found it best to have the channel going down the side and along the bottom with some air vents coming out of the top. Always try to angle any pieces so there aren't any corners that bubbles will get trapped in.

6. Indentations and a simple solution
When it came to creating my first mold I noticed that I'd sculpted some recesses that were going to cause a massive problem, then I had a brainwave. Using a bit of green stuff I created some little plugs that are molded to the recessed area and a hooked area at the top. When you create the mold halves, make sure this piece is sitting in the recessed area properly. When you go to create an actual cast, carefully place the plugs back into the now empty mold so that they will allow you to create recessed areas that a 2 part mold wouldn't normally like.  They easily pop out and leave you with a recessed area. *tada!* I wouldn't suggest using too many things like this though as you're bound to forget to put them in (like I did for test cast 2) and you end up with an odd hooked lump on your piece. You also need to remember to put a little bit of vaseline on this, otherwise the resin can stick to the greenstuff plug.

7. What about all these rubbish test molds?
You don't need to throw them away. Keep them; slice them up into little bits and put them around the edges when pouring in your RTV to create a new mold. As long as there's no release agent or vaseline on them they will stick to the new rubber, bulking out the mold and saving you some precious rubber

What else?

A number of people recommend vacuum chambers or pressure pots. If you're only doing basic, fairly plain things I don't think they are necessary. They may, however, be the answer to me getting more detailed casting... though it's rather expensive to shell out a couple of hundred pounds on a theory. A vibrating plate that you sit the molds onto would help to bump some of the bubbles out of your mold. Poundland occasionally has "personal massagers" that would be good for making something like this