Thought I'd contribute this little article I've written for those that are seeking an alternative to Sculpy as a sculpting medium when designing toys. For the most part I will cover how to work with Casteline wax and the tools and techniques I've used.
What is Casteline? Casteline is a fairly new sculpting wax that comes in three different hardness (soft, medium, hard). It's self supporting so there is no need for an armature and aside from the more rigid Azbro wax it is the second choice for sculptors as the medium for prototyping work in the toy design industry. It only takes a small amount of heating (hair dryer/heat gun, light bulb/heat lamp, heat from your hands) to get Casteline to work like clay. There is no baking involved so it's ideal for when revisions to the sculpt is required. This is the reason why toy companies reject prototype work done in polymer clays or any material that are difficult to revise with relative ease.
Why use Casteline? Unlike traditional rigid sculpting wax, Casteline when heated becomes malleable like clay. It's a great transition from polymer clay specially when used as a sculpting medium for toy design and other prototyping applications. You can make any revisions with Casteline no matter how drastic or simple that maybe without re-baking like polymer clays and risk cracking you hard work. You just need a few extra tools to work with wax but the benefit is well worth it. Lets start.
You'll need some basic tools (some you may already have) specifically needed to work with any type of sculpting wax. Small crock pot (available at any Wal-Mart) for melting wax into sheets, metal sculpting tools (metal cause you will need to heat it), electric wax pen (optional), alcohol lamp/burner, alcohol torch, and clay shapers (optional). I'll cover other incidentals as I go along so please do read on.
metal sculpting and dentist tools
As I've already mentioned, armatures are not needed when working with Casteline. To save on material however you should use a filler like crushed tin foil. I usually start with a basic form using hard Casteline and switch to medium to build it up and for detail work. Soft is too fragile for me and I for the most part do not use it. Casteline comes in 2.5 pound tubs. When you have purchased your wax you should prepare it for use by melting it into sheets. Use a standard crock pot dedicated for wax use, once you use it for wax you can't use it for preparing food anymore.
Casteline wax in sheets
Melt the wax using the high setting on your Crock Pot until most of the wax becomes like soft semi melted ice cream then switch to the medium or low setting depending on how hot you pot gets. The idea is to melt the wax without boiling it. Casteline will separate so keep an eye on it and keep stirring it, making sure to scrape the bottom. Casteline has a caramel like smell that some folks like or hate so make sure to do this away from your common area just incase. Prepare a flat baking pan (or two) lined with tin foil. Once the wax is completely melted, pour the wax onto the pan/s into sheets (make sure to completely stir the wax scraping the material that has settled to the bottom before pouring or you will have some inconsistencies in your wax. Be careful not to burn yourself and use pot holders or better yet foundry type gloves. You can also use a ladle to scoop out melted wax but this takes too long for me. Do this to the entire content of the tub. If you're using different hardness make sure to scribe the hardness on the sheets to keep track of them. I keep the wax sheets I've prepared dust free in zip lock bags...So now that your wax is ready and your burns have healed (kidding) lets start sculpting.
Start off by balling up some aluminum foil as a filler to avoid wasting wax. Assuming you have and are working off of a set of drawings, proceed on to generate you basic form by breaking off strips of wax from the wax sheets you prepared before hand. Heat the strips to a malleable state and build your form in layers. I have used hair dryers and heatguns for this application and they both work fine at warming the wax. You can also preheat them by having the wax sit under a bulb lamp but I found the hair dryer/heatgun system is more convenient for me. Hand warming will also work on smaller pieces. Working with Casteline will be like working cold extra firm Sculpy. It may feel like it's fighting you at first but you'll get use to it. Just be patient and take your time with the basic form since this is where you will build you detail on.
alcohol burner and torch
Smooth the surface by using a sculptors spatula or something similar heated over an alcohol burner. Your burner and torch should be filled with nothing other than denatured alcohol. It burns clean and hotter than plain candle flame. I usually use hard Casteline for the basic form and then switch to medium hardness for fleshing it out and detail work. Work like your doing a sketch, rough form slowly working into a more defined shape and tighten up the line as you go. Once you have established a relatively smooth basic form you can move on the flesh it out, smooth again, add even more fine details and repeat. If the whole sculpture is too soft where it get bruised by handling then place it in the refrigerator for a few minutes to cool. I have a habit of leaving fingernail marks because I man handle the piece when I work on my sculpt that I make sure I trim my nails down as short as possible before working. That's another great thing about Casteline, you can place a reasonable grip on your work without leaving finger prints and negating the need for a sculptors turn table stand unless you're working on a very large piece. Not happy with the angle of the arms? You can easily fix that by heating the elbow area with a hair dryer/heatgun (careful not to melt your details out) and bending it to the desired angle. You can't do that with cured Sculpy without fracturing and doing a major re-sculpt then re-baking the whole thing and risking further cracks.
metal tipped sculpting tools
Foredom wax carver
As you move on to tightening up your work and adding finer details you will need the use of your metal sculpting tools. You probably already have some favorite tools that you use when you worked with polymer clays. If you want to switch to Casteline type waxes you will need sculpting tools that can be heated over an alcohol burner. You should be able to find metal versions of your favorites without any problems. Some slight alterations will inevitably be needed in your sculpting technique but this should not be too far removed from what you're used to and you may be pleasantly surprised at new ones you develop. One favorite tool of mine are ball tipped sculpting tools that I use for smoothing/blending/merging on added details. Just heat the tool for a few seconds tops (heat longer as needed but try it out on scrap pieces first specially when experimenting). For bigger jobs where continuous heat is required or when removing a substantial amount of material, a jeweler's wax pen (with a large spoon tip) would be a worthwhile investment. This is also ideal for adding stippling and other surface effects depending on the tip being used.
Silicone tip clay shapers
D-Lemonene
Aside from traditional sculpting tools, I've also found metal dentist tools (easily found in eBay or local flea markets) to be very useful and inexpensive. Another tool I've recently discovered are silicone tip clay shapers. These tools resemble paint brushes but with a silicone tip (wont stick to your work) that comes in different shapes and firmness. I use the black extra firm tips for wax use. Use it on warm areas as an extension of your finger tips for those hard to reach areas. When you're ready to buff or polish Casteline, a small amount of D-lemonene, Goo Gone, Mineral Oil, Citrusol, Wintergreen Oil or a dab of petroleum jelly (Vaseline) on a discarded piece fine mesh lady's nylon stocking works great. A little goes a long way and too much of any of the above mentioned will result in an orange peel like texture on your sculpture so go easy and start on an inconspicuous area. Personally I like to use an alcohol torch to put a quick polish on the surface. This requires a complete familiarity with an alcohol torch and it's effect on wax so get used to using it first on scrap pieces of wax to get your finesse with the torch established. Also keep in mind that your sculpture can have a nice finished surface with plain old buffing by your own hands and tools. The sculpture I'm currently working on is untouched by any of the polishing/buffing chemicals/compounds I've mentioned. Just my hands, tools, and patience.
Casteline and silicone RTV compounds: Since Casteline is specially formulated for prototype use, it is completely compatible with virtually all brands of silicone mold making compounds. There are pretty much no changes in the way you would normally generate molds for masters done in Casteline wax. Just keep in mind that it is wax and not a rock hard piece of cured polymer clay that you're working with this time around. Make sure your sculpt has had a chance to cool completely to assure that it's completely hard and ready for mold making. This is specially true when you're partially imbedding your sculpt to generate mold halves.
I hope this little article has been helpful. Casteline isn't for everyone but hopefully you'll find what I've written compelling enough to give it a real try. I switched shortly after I first discovered it a few years ago and never looked back. It's worlds easier that traditional prototyping wax like Azbro and makes a perfect alternative to traditional and polymer clays for toy design applications.
You can purchase Casteline, D-Lemonene, Foredom wax pen and other wax sculpting tools @
http://www.sculpt.com/ . Accept for the Casteline wax itself all the tools and liquid solutions mentioned in the article may also be available at you favorite art/hobby supply shops, local hardware stores and places like good ole eBay.