Tuesday, 20 September 2011

Figure Sculpting: Epoxy Putties - Greenstuff or Kneadatite Blue/Yellow

Miniature sculptors, generally, either use two part epoxy putties or polymer clays.

First off, I am going to look at epoxy putties and with this article the mainstay of figure sculpting for many years, "Greenstuff".

Duro StickKneadatite Blue yellow

Epoxy Putty is supplied in two parts, a filler or body and a hardener. You mix together the two parts and after a period of time the putty sets. There are many different varieties of epoxy putty that are suitable for sculpting with, but they broadly fall into two types, hard set putties and flexible set putties. As the names suggest when these putties have set, they are either hard, which is easily machine-able and sand-able or flexible which retains a plastic type flexibility.

Professional figure sculptors have preferred flexible putties for many years due to production requirements. Basically, the process involved in taking a finished sculpt and turning it into a production run figure usually involves placing the figure between two layers of  rubber and applying heat, around 300 degrees centigrade, and pressure to press the softened rubber into the figure. This is called vulcanising the rubber. Once allowed to cool and set, the original sculpt is removed leaving a cavity into which the molten metal can be poured.

If the figure is sculpted with a hard putty it is far less likely to survive the vulcanising process, getting crushed under the pressure, possibly ruining the mould and leaving you with nothing to work with at the end.
There are other mould making techniques that can be used with different materials, but generally they add an extra process and this adds to the cost of production. I will look at mould making techniques another time.
The main putty that has been the industry standard in miniature figure sculpting for many years is Kneadatite Blue-Yellow, produced by Polymeric Systems. It is  sometime referred to as Duro. Kneadatite is actually a plumbers repair putty but was discovered as a sculpting medium and developed by Tom Meier, when Ral Partha, the miniatures company Meier helped found, were looking for an alternative to lost wax casting in the early 1970's.

Kneadatite Blue/Yellow is a flexible set putty and comes in two parts, one yellow and the other blue. When mixed together the two parts blend together and the putty goes an even green colour. Kneadatite Blue-Yellow is often referred to as Greenstuff within the hobby, due to it’s colour, once blended.

This is also where the term for finished sculpts that have yet to be cast comes from, they are correctly called a Master but are more commonly called “Greens”.

Three "Greens". Notice that the weapons are sculpted with Kneadatite Brown/Aluminium.

The Kneadatite is generally mixed in a 1 to 1 mix, although, as with many of the different putties, different sculptor favour slightly different mixes, some preferring a 60:40 mix of blue to yellow, and others preferring it the other way around. These different mixes affect the setting time, the texture of the putty and also the properties it has once set. So clearly experimentation and experience are need to find the mix that suits each sculptor.

Kneadatite Blue-Yellow is available as either a ribbon (approx. 1metre/1Yard long) or as two sticks. The disadvantage of the ribbon is that the two components are touching and so there is always a small amount of putty that sets where the two parts touch. This means that you have to be very careful to cut the set “lumps” away before mixing your putty together.

Polymeric Systems used to make another of flexible sculpting putty, Kneadatite Blue-White. The blue-white putty remained white once it is blended together, I found it had a different consistency to greenstuff and didn't really enjoy working with it as much. Also due to the colour, it was actually harder to see the detail you are sculpting when compared to working with greenstuff.

Kneadatite Blue White

Somewhere in-between the hard and flexible putties, Polymeric Systems also make Kneadatite Brown/Aluminium (Brownstuff ?). This putty is certainly harder than Blue/Yellow, and it files and sands fairly well. I have used this for weapons, as it has a similar sculpting feel to greenstuff, but sets that much harder and can be filed to get a good edge. As the name suggests, one part of the mix is a brown in colour and the other has a silvery metallic colour. Once mixed it remains brown but with something of a metallic fleck though it. I like using Kneadatite Brown/Aluminium as it for the jobs that might well need filing to an edge. The putty is very easy to use and is easy to clean up with no deposits remaing on your hands. As I suffer from some skin irritation when using certain epoxy putties (I have to wear gloves when handling Milliput, A+B etc.) it is always useful to find a putty that doesn't cause any dermatological problems.

(Note: Since writing this article I have found out that Brown/Aluminium formula has been change and is now called Brown/Neutral. I cannot vouch for the properties of the new formula as I haven’t used it, but I would imagine that it is similar to Brown/Aluminium)


Now is where it all gets complicated, many professional sculptors mix different varieties of putties together to achieve different properties. I have regularly mixed greenstuff with a little Milliput, to give me a sand-able finish that is more resilient than straight Milliput.
Also, recently I have been adding a little Fimo polymer clay into my greenstuff mix. At around 10% (you don't want too much polymer clay in the mix or it wont set), it lengthens the setting time and makes the greenstuff slightly softer to work with without noticeably affecting the set strength of the greenstuff.
Again, it really comes down to experimenting with different mixes until you find what you are looking for.

In my next look at sculpting putties I will move on to Pro-Create. It share some similar properties to greenstuff, but also has some advantages over it.

For further information on sculpting putties and figure sculpting in general, I recommend anyone interested signs up to the 1listsculpting mailing list at Yahoo-groups.
Also for a look at a selection of sculpting putties, you can visit Sylmasta.com, this UK company supplies many of the different putties available. 

For more information on the Kneadatite putties, and also to find out about local suppliers you ca contact Polymeric Systems at this address:-

Polymeric Systems, Inc.
47 Park Avenue
P. O. Box 522
Elverson , PA 19520

Tel: (610) 286-2500
Toll-free in the U.S.
800-CAULK IT (800-228-5548)
888-EPOXY FIX (888-376-9934)
(610) 286-2510


In the EU contact:

Whitford Plastics Ltd.
10, Christleton Court , Manor Park
Runcorn, Cheshire WA7 1 ST  UK

Tel: +44(0) 1928 571000
+44(0) 1928 571010

1 comment:

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