Casting your own parts may seem quite hard and best left to the after market guys. But you will be suprised how simple it is to get good results. It also opens up what you are able to do with your kits and dioramas.  From casting extra ammo boxes and replacing lost parts to building complete original models from a master.

The following will be a simple walk through of casting a wheel for a 1/48 aircraft. The part was lost so a copy was needed or the project had to be shelved.

STEP 1

The part, in this case a wheel, was assembled and cleaned up. Any seams or burs will come out in casting. It should be finished to off how you want the final cast part to be.

Step 2

Next a plastic mounting block is made for the part. This raises the part slightly and provides a channel to pour the resin. Also when removing the part from the mould you can use pliers on the block without damaging the part. A mould box is made up of scrap plastic card. This will contain the silicon rubber to form the mould. The box should be at least 10mm higher than the highest point you will cast. The sides should also have at least 5mm gap around the part to be cast.  The larger the part (ie. a tank hull), the thicker the mould walls will have to be as when large amounts of resin are poured, it puts pressure on the mould and it deforms it. The mounted part can then be lightly tacked with super glue into the mould box. This helps recycle the mould box as it can be broken down and reused for another project.

Step 3

The silicon I used used for the mould is a very user friendly material.  Available from AMT Natal ( 031-201 1219) Called Mould Max 30, it has about a 10min mixing time and cures in about 4 hours at room tempture. The catalyst is about 10% mix but I always use more and now has a pink/red tint to help mixing.

Estimate how much silicon you will need and pour it into a mixing cup. Alway have too much rather than too little. Add the catalyst and stir. No need to rush as you have got time and you don t want to add too many air bubbles. After a few minutes the material will change from a white colour to a uniform pink colour. Once this happens you need to pour.

STEP 4

Start in a corner of the mould box and pour the silicon in a thin stream. The thin stream helps push out air bubbles. Let the material follow its own flow, don t try to rush it. As the silicon flows, it fills up the box from the bottom so as not to trap air in unwanted areas. When filled to the top, small air bubbles will apear on the surface, this is ok as you want them there and not on the surface of the part.

STEP 5

Once the master patten is removed from the cured mould, the resin can be prepared.

Again the materials are supplied by AMT Natal. Above are the two part resin, filler to extend the volume of the material, mixing cup and hypodermic syringe to help get resin into tight spots.

The resin is called Fast Cast. Mixed in a 50/50 ratio it has a working time of 90 seconds. Will gel in about 5 minutes and cure in 45 at room tempture. Its volume can be increased by adding a filler so large projects take up less material. It can be sanded, glued with superglue and takes paint well. If there is material skrinkage I have seen none in all the project I ve done.

The mould does not have to be prepared. I do not use any release agents, just make sure its free of dust. Pour the two components of the resin in equal parts into a mixing cup. MIX till a creamy colour. 90 seconds is longer than you think but rather not waits too long as you want to be able to pour the resin while its still water like. Again pour it in a thin stream to remove bubbles. The plug hole in the mould will help channel it in. Also the mould can be squeased gently to help remove any trapped air.

Once the endothermic reaction start, you will feel the material start to heat up. Large pieces can get quite hot but this will only be a problem if air is trapped in the resin and as the heat expands it your cast will deform.

STEP 6

After 45 minutes you can demould. Gently break the seal between the cast piece and the mould by streching the silicon. If its a bit stubbon, pliers can be used on the pour plug to help remove with out damage to the piece. Remove the pour plugs with a knife and sand paper.

A few tips I ve learnt... A mould can last for years. But will degrade every time you cast so keep you masters if possable.

Single part moulds are easy and yeld better results so try break a complicated project down into simple sections for ease of casting and mould making.

A light dusting of the moulds with talc or the filler will reduce air bubbles and help the resin get into small places.

Very small moulds can be difficult to pour, use a syringe to inject the material.

Nothing is impossiable till you try it...

Resin Ammo Trailer 1/35 original production

WWII SS Oak Leaf "A" Camouflage, Summer (Brett Avants)

VC-825 German Camo Pale Brown
VC-850 Medium Olive
VC-862 Black Grey

Base: VC-825

WWII SS Plane Tree Camouflage (Brett Avants)

VC-822 German Camo Black Brown
VC-825 German Camo Pale Brown
VC-833 German Camo Bright Green
VC-857 Golden Olive
VC-929 Light Brown

Base: VC-825
Highlights: VC-929
Shadows: VC-822
Dark Spots: VC-822
Light Spots: VC-857
Dark Green Fields: VC-833

WWII German Gebirgsjäger Anorak (Brett Avants)

VC-862 Black Grey
VC-887 Brown Violet
VC-992 Neutral Grey

Base: VC-887 + VC-992 (2:1 Ratio)
Highlights: VC-887 + VC-992 (1:2 Ratio)
Light Highlights: VC-992
Shadows: VC-862 + VC-887
Deep Shadows: VC-862

WWII German Field Grey #1 (Brett Avants)

VC-830 German Field Grey
VC-862 Black Grey
VC-886 Green Grey

Base: VC-830
Highlights: VC-886
Shadows: Base + VC-862
Deep Shadows: VC-862

WWII German Field Grey #2 (Brett Avants)

VC-830 German Field Grey
VC-868 Dark Sea Green
VC-886 Green Grey
VC-950 Flat Black
VC-979 German Camo Dark Green

Base: VC-830 + VC-868 (1:1 Ratio)
Highlights: VC-886
Shadows: Base + VC-979
Deep Shadows: VC-950

WWII SS Palm Camouflage (Brett Avants)

VC-805 German Orange
VC-822 German Camo Black Brown
VC-833 German Camo Bright Green
VC-929 Light Brown

Base: VC-929 + VC-805

WWII Waffen SS Pea Dot Camouflage, Fall (Brett Avants)

VC-835 Salmon Rose [substitution for Liquitex Deep Portrait Pink]
VC-988 Khaki
VC-825 German Camo Pale Violet Brown
VC-822 German SS Camo Black Brown
VC-833 German Camo Bright Green

Base: VC-835

WWII Wehrmacht Splinter Camouflage #1 (Brett Avants)

VC-821 German Camo Beige
VC-825 German Camo Pale Brown
VC-969 Park Green Flat
VC-980 Black Green

Base: VC-821

WWII Wehrmacht Splinter Camouflage #2 (Gray Creager)

VC-821 German Camo Beige
VC-826 German Camo Medium Brown
VC-823 Luftwaffe Camo Green
VC-896 German Camo Extra Dark Green

Base: VC-821

WWII Wehrmacht Splinter Camouflage, Marsh Pattern (Brett Avants)

VC-821 German Camo Beige
VC-825 German Camo Pale Brown
VC-892 Yellow Olive
VC-980 Black Green

WWII USMC Fatigue Green (Brett Avants)

VC-830 German Field Grey
VC-886 Green Grey
VC-971 Pastel Olive Green

Base: VC-886
Highlights: VC-971
Shadows: VC-830

WWII US M1941/43 Khaki Field Jacket (Brett Avants)

VC-837 Pale Sand
VC-988 Khaki
VC-914 Green Ochre
VC-976 Buff

WWII Deutsche Afrika Korps Tunic (Jaume Ortiz)

VC-819 Iraqi Sand
VC-888 Olive Grey
VC-950 Flat Black
VC-978 Dark Yellow

Base: VC-888 + VC-978
Highlights: Base + VC-819
Shadows: Base + VC-950

WWII Deutsche Afrika Korps Trousers (Jaume Ortiz)

VC-819 Iraqi Sand
VC-872 Chocolate Brown
VC-914 Green Ochre

Base: VC-872 + VC-914
Highlights: Base + VC-819 + VC-914
Shadows: Base + VC-872

White Uniforms (Brett Avants)

VC-820 Off White
VC-862 Black Grey
VC-907 Pale Grey Blue
VC-950 Flat Black
VC-951 Flat White

Base: VC-820
Highlights: VC-951
Shadows: VC-907
Deep Shadows: VC-907 + small amount of VC-950
Deepest Shadows: VC-862

(reference found by Paul Tzacos)

http://www.missing-lynx.com/articles/other/modulationmr_1.html

http://www.migproductionsforums.com/phpBB3/viewtopic.php?f=5&t=3293

LIGHT BASE AND INCREASE

This is a basic technique that can be used in cars or monochromatic camouflage those who possess it but is in such a way that there are large areas of a given color. The application of "lights" or "rises" produces an increase in volumes and it avoids the surfaces, especially large ones, are dull and flat. " The paint application is done with airbrush. We started by covering the entire model (in this case a Sherman M4A3 (76) Hobby Boss 1 / 48) with a dark shade that will serve as initial and as primer. In this case, as the base color is Olive Drab XF62 (Tamiya acrylic), the dark shading is done with a mixture of olive drab and black. The next layer is the base color itself is Olive Drab XF62. Although it covers most of the previous layer, we must ensure that the "presombreado" is noticeable in the corners and lines of demarcation panel. The following is a first ascent with a mix of Olive Drab XF62 and XF60 Dark Yellow.  To clarify the color green is better not to use white, but color of a range of ochres like this. This blend is mainly airbrush in the center of the panels and surfaces, the previous color showing at the edges. If desired, you can make a second ascent, further clarifying the base color, and applying this second mix is even more restricted in the center of the surfaces. It is as if painted concentric spots increasingly clear and smaller. This model does not implement a re-raise because it would receive camouflage. The camouflage is broadbanding color black XF1 unclear. Since the bands are wide and occupy a considerable area, you can make them their own "rise."  For this I used XF69 Nato Black, actually a dark gray with a greenish hue. This car is ready for the next phase would be the application of trademarks, either in the form of decals, transfers or painted. Although you can give the impression that the increases were very marked, the transitions between them are smoothed by the following treatments (filters, washed, mapping ...)

Purpose
- To instill a level of contrast on the model surface/detail using a greatly thinned paint
- To darken the corners and recesses on the model
- To give a realistic appearance of the portrayed model, a worn out look.

Recommended paint and thinner
Paint - Artist s oil paint or flat hobby enamel
Thinner - turpentine or mineral spirits

Procedure
- Make the wash by mixing a small amount of dark colour paint with lot of thinner

- About 10% paint, 90% thinner
- Use a darker tone of the basic colour used on the model.
- Example: if your basic colour of your model is gray, then use dark gray or black for the wash mixture. If your basic colour is dessert yellow, then try using dark brown

- Apply the wash over the surface with a wide, soft brush
- Let it flow into the corners and recesses of the model
- The capillary action will run the wash along engraved lines and around raised details of the model surface.
- Remove the excess wash with a dry brush or tissue while the wash is still wet

Hints for washing
- Complete all paint jobs on the model and application of decals before proceeding with the wash.
- To prevent ruining the paint work, give the whole model a layer of clear matt coat before applying the wash.
- You can further darken the colours of corners and recesses of the model with a more concentrated wash (20-30% paint and 80-70% thinner)

- Apply it only around the area that is needed with a sharp pointed brush (Also known as localised washing.)