I found this article detailing important notes on the intrinsic colouration of silicone and thought it prevelant and found it suitable for this project. I have highlighted the important aspect of the article for ease of access. 

 

IMPORTANT NOTE ON THE INTRINSIC COLOURING OF SILICONE:

 

The best paint job should complement the colour of your silicone, not completely hide it. Painting silicone isn’t like painting foam latex or latex, where you are starting with a very unnatural flat dead appearance and trying to bring it to life. In fact there isn’t a lot of point using silicone for pieces if you aren’t going to take advantage of the very flesh-like translucency it inherently possesses. So the crucially important step is to tint your piece intrinsically before you cast it, to give your piece the best and most lifelike tones onto which you can then paint your ‘skin’ surface.

 

Either use proper silicone pigments, and flocking, or a mixture of both. You don’t want it too transparent, nor totally opaque. Think about the piece you are making and about the real object, and try to match that amount of light permeability. For instance, your hand is pretty translucent when held up against a very strong light, your arm less so, and a skull barely at all.

 

You can use oil paints, but test first- some colours change as the silicone cures, and some react badly and inhibit certain silicones. You may be better to just buy a silicone pigment, its not going to cost much and a little goes a looooong way… You can also just tint the skin of the piece, stippling or brushing that into the mould, and then backfill with plain silicone.

You can use flocking on its own, which is one way of adding colour and breaks up the 'flatness' of a pigmented piece, and is a cheap-ish way of intrinsically coloring silicone dependant upon the size of the piece.

 

 

In terms of colour choices, avoid anything with orange tones. You'll fight against them later when you do the extrinsic painting. Go pinkish or pale reds. The best "off the peg" flesh tone Neill has recommended is a Liquittex liquid acrylic colour called "Sandalwood".   Obviously you cant use acrylics in your silicone but if you can use that as a reference colour  to get or mix a pigment to match that, then you'll be off to a good start.

 

To achieve a realistic translucency, until you are familiar with the process you should either test small samples as you go along, just 20gm batches at most, by catalysing them and placing them in your mould or a similar mould so you can see the final result with the surface texture.

When mixing the pigment into the silicone you can use a wooden mixing stick with a small black or blue dot or vein pattern drawn on. As you mix you dip the stick in and let the silicone drain and see how the dot or lines are showing through. If they're crystal clear then you're way too translucent, if they're invisible then it’s much too opaque. If you can see the dot or line but its very soft then that'll be just about right.

 

PAINTING SILICONE PIECES:

           

WHAT MATERIALS DO I NEED?:

 

 

1.  A SILICONE BASE or CARRIER 

Your options are:

·      Dedicated silicone painting systems

·      Silicone caulking,

·      One-part acetic-cure silicone.

 

A dedicated silicone painting system comes with a two-part silicone base system and custom pigments. Examples include Fuse FX, and Psycho Paint. While these certainly work very well they are expensive and you may not be able to afford them when starting out. Also, they are both platinum based so you can ONLY use those on platinum cure (addition cure) silicones, NOT on Tin silicones.

 

Silicone caulking is sold as window or bathroom sealant. In a long cylindrical tube that is usually used with an applicator. It is a single component Tin silicone that cures by exposure to air and moisture by acetic acid reaction, and it "bites" into the surface of your piece much better than using a two-part silicone mix.

One-part acetic-cure silicone is the clear leader and industry favourite. What you want is the type of silicone in a small tube from the hardware that is used as a sealant or adhesive and sometimes known as gasket silicone. It is a single component air-and-moisture activated Tin silicone like caulking, but it has a higher proportion of acetic acid so it bites better and sets faster. Popular brands are ‘Dow Corning 734 all purposes silicone glue’, ‘Wacker Elastosil A07 Flowable Adhesive’, ‘3M RS Silicone Rubber Compound’, “GE 1200 clear”, “Smooth-on Silpoxy” etc. Also use a decent quality silicone sealant. Cheaper products will always give results equivalent to their price.

*Both Silicone Caulking and Silicone Adhesives can be used on both Platinum or Tin silicones.

 

WHY CANT I JUST USE THE SILICONE I MADE MY PIECE WITH?

 

It is certainly not totally impossible, under ideal conditions, to get a half-decent finish using a two-part silicone such as you already used to make the piece, but it is definitely more difficult, because you are adding other components (pigment and solvent) which can (and will) interfere with the setting and bonding.

2 part systems (eg Platsil Gel 10, Dragon Skin, Eco Flex, etc.) use a catalyzation chemistry to cure. They've been especially formulated to crosslink, which means that the molecules in each part interact as soon as they make contact with the other component and over time they ‘set’. If you introduce foreign elements or the conditions aren’t right, those molecules never get to grasp each other properly, and you have sticky tacky unset jelly.

There is more flexibility and room for error when using a dedicated painting formulation, or a single component system. They will adhere better and dry faster with less risk of delamination. Caulking and silicone adhesives are an acetoxy cure system, so what happens is that the moisture in the air reacts with the solvent in the wet adhesive as it evaporates, which forces the molecules to lock together. Both caulking and silicone adhesives have a very distinctive ‘vinegar’ smell, which is the acetic acid in them.

 

 

2. PIGMENTS

 

Your options are:

·      Silicone Pigments

·      Oil Paints

·      Inks

·      Acrylic paints

 

Silicone Pigments are designed to colour silicone intrinsically, and are unlikely to inhibit your cure unless used in too-large quantities. Remember though that pigments are NOT silicones themselves and will NEVER cure on their own. They MUST be used in a base.  There are some that are better for painting than others with better colour choices and more realistic shades for skintones. Mouldlife make a great selection. They may seem pricey but a little goes a long way. Be careful not to dilute the silicone too much- it's easy to end up with mostly solvent on the brush when you mix the pigment in and end up with a mix of solvent and pigment, which will never dry completely....

 

Oil paints ore ok and commonly used, but, oddly enough, oil paint can have oil in it! Also there are other impurities that can inhibit the cure.  Be aware that even within the same range there are different minerals used for pigments that can affect setting, and some that react strangely to silicone and actually change colour. Use too much, or too much of the wrong color and you are back to goo...  Some cheaper oil paints are not going to give a good result, always try and get a reputable brand. Also oil paint on its own will set, but veeeeeerrrrryyyyyy slowly, (think days and weeks, not hours..) and it will not bond to the silicone on its own. The way to avoid this is make sure you don’t use too much solvent when painting, or you end up with no silicone in the mix and just a smeared mess of wet oil paint on your surface instead.

 

 

Inks can be used in some cases, mostly dependant upon the final use of the piece. Skin Illustrator inks are used on Super-Baldies encapsulated silicone pieces and also can be used on straight silicone pieces that are going to be used only on the body and painted in situ, as you cant use toxic solvents near a person. FW Inks are popular to airbrush over Silicone. The way to have those colors permanently fixed is to seal it with one part Silicone caulking thinned down with a fast solvent, such as Heptane, between each one or two ink colors. Bluebird Inks can also be used for intrinsically colouring the silicone, and surface painting in the same way as FW Inks.

 

Acrylic paint is a last resort. It can have odd effects on the silicone and make it ‘curdle’, so if you have to use it test test test! Also it WILL SPEED the cure time of silicone caulking so may require a thinner to counteract that. Best avoided.

 

 

3. SOLVENT

 

Your options are:

·      Petroleum Distillate of some type.

·      D-Limonene

·      Dow Corning OS-10 fluid

 

 

Petroleum Distillates have been used as industry standard for years, but require special precautions for use as they are amongst the most toxic things we use. Proper Personal Protective Equipment is mandatory. It will, very literally, put you in hospital if you fail to wear adequate respiratory protection.

 

The family of petroleum distillates, or hydrocarbon condensates, includes many different chemicals- make sure you look for the ‘UN number’ on the bottle. It will be a clear chemical, and have 'flammable' written on the bottle or tin- basically anything with an N number (Hazardous goods identifier) between 1200 and 1300! Naphtha is UN1268, as is some liquid lighter fluid and some white spirits.

There are numerous different types with different names in different countries and from different refineries. They are sold in hardware stores and automotive stores as fuels, cleaning or degreasing fluids, or car panel wipe.

Essentially it will always have a red label saying FLAMMABLE 3 on the bottle somewhere. May be called: petroleum ether, petroleum spirits, ‘Coleman’ brand stove fuel, ‘Zippo’ brand lighter fuel, mineral spirits, paraffin, benzine, hexanes, heptane, ligroin, white oil or white gas, painters naphtha, refined solvent naphtha and Varnish Makers' & Painters' naphtha (VM&P)

 

 

To say it can be terribly confusing for people in different countries trying to find the local equivalent is the understatement of the year!! 

For instance, ‘Naptha’ is often referred to as the preferred solvent, but ‘Naptha’ is a generic description rather than a brandname, and for instance, in Australia, it is labeled as “Shellite’ (after one manufacturer), or White Spirits.

‘Zippo’ brand lighter fluid is widely available, and is basically pure Naptha, however it's a mixture of a heavy and light weight Naptha distillate, which allows it to be less susceptible to evaporation than some forms.

Regular White Spirit takes forever to dry. Use LOW ODOUR white spirit which is a lighter grade of Naphtha, it's purer and faster drying.

As you can see, ‘Naptha’ can be a misleading ingredient to find on the side of the bottle. It is often used in a paint shop, but the preferred type there would be VM&P (varnish makers and paint) grade Naptha.

*We recommend you DO NOT use  older solvents such asToluene without the best protective gear available. It is highly HIGHLY toxic and needs special safety gear.

 

ALL solvents should only be used while wearing respiratory protection classified for the solvent you are using, and other appropriate PPE.

 

 

NON TOXIC ALTERNATIVES:

For many reasons there are situations where you either cannot use a toxic volatile chemical, perhaps for OH & S reasons, or location, and in some places you cannot even buy them easily. They are difficult to transport, and hazardous to store, and if you already suffer from any health issues (or if you wish to become a parent in the near future), they may be best avoided wherever possible. If you are looking for a non-toxic alternative for safety or personal health reasons, you are in luck!! Unlike people working ten years ago, we now have a couple to choose from!

 

D-limonene is a far less toxic alternative solvent, and is available in many countries in hardware stores or specialist cleaning supply houses. It is classified as GRAS (generally regarded as safe) and non-toxic and is pleasant smelling. It is derived from citrus peel.  D-Limonene is often used as a degreaser and cleaner, it is also used as a flavouring agent and can be purchased in food-grade qualities.  It is suitable for use in smaller spaces and if you don’t have a properly vented paint booth,

Dow Corning’s OS-10 Fluid is a totally volatile organic compound free ozone-safe compound that can be used for a variety of applications. Non toxic, colourless, odourless, and safe if you have to work in an enclosed space without adequate professional ventilation systems.  Works on both tin and platinum varieties and dries to such a minute thickness that it still shows every detail of texture. Works on just about any of the silicone systems. Low smell, quick drying, and you can also mix oil paints in to caulking and thin it with the OS-10.   In the States Burman Industries supplies it, in the U.K. tryhttp://www.ellsworthadhesives.co.uk/index.php/dow-corning-fluid-os-10-2-8kg-clear.html  They also make one called OS 30- the number represents the speed in which the solvent flashes off and out of the silicone itself, which may be useful if you are doing a bigger project such as painting a creature suit with silicone that was intrinsically colored. Hypothetically the 10 should flash in ten minutes and the 30 half an hour more or less, according to ambient temperatures. You can also use it as a thinner to to spray silicone through a spray gun like you would Super Baldiez... or an air-brushThere are some primer measures and steps involved, but the OS series has also been used by people to help coat big foam latex creatures and such with tin silicone...

An alternative option is ‘Silicone Solvent’ from Reynolds Advanced Materials/Smooth-on.  It is the same or similar formula, consistency, and results.

 

*Isopropyl alcohol and acetone are NOT suitable solvents.

 

 

HOW DO I USE THEM?

 

Explanations are great but they can only go so far. For some of you it is undoubtedly going to help enormously to see someone demonstrate the technique before you attempt it on your precious work, which you have struggled and slaved over to get to this point. You don’t want to come this far only to mess it up now!

There are a couple of great tutorials available online, they are both paid access to stream the video, and you can also purchase a DVD if you prefer.

Both are well worth the small price to ensure your success:

 

Neill Gorton has a great instructional demo here:

 

http://shop.mfxwarehouse.co.uk/dvds/dvd-s/the-art-of-silicone-prosthetics/dvd-4.-casting-finishing-and-application.htm

 

 

Also Stan Winstons Studio demo:

https://www.stanwinstonschool.com/videos/silicone-painting-realistic-flesh-tones-vol-1                       

 

1. CLEANING & PREPARATION

 

In a perfect world you want to paint your piece as soon after casting as possible as the fresher the silicone the better the bond. Also make sure the surface is very clean and dry. Technically the process of painting silicone is laminating, as you are applying layers of silicone on top of the piece itself, and those layers bond to and become an integral part of the piece itself. This differs from true painting in that it is not a separate surface layer that can be removed. As with all lamination, the colouring will only stay on if you have cleaned the area thoroughly of any remaining release agents, sticky fingers, dust or airborne contaminants. You want to wash your piece with warm soapy water after de-moulding, then give it a good clean with 99% Isopropyl Alcohol. Allow to dry thoroughly.

That should be all you need to do.

 

 

If however your piece has been sitting around in the open for a while or you have used a particularly stubborn release agent, you might need to bring out the big guns. (This also applies if you have attempted to paint it before you read this information and it was less than a success!)

 

Your first attempt should be a quick but thorough wipe with acetone and then a quick wipe with Naptha or lighter fluid, which dries without a residue.  Finally, do a 99% Isopropyl Alcohol wash and it should be clean as a whistle.

 

If that doesn’t work for some reason, you can move up to Heptane, which is much stronger, and is available as rubber cement thinner in good art shops.  Mixed 10:1 with silicone adhesive this primes the surface, and it will stick over almost anything, it dries relatively quickly but a heater in the room if its cool speeds things up.  Then when that’s dry you can do  a layer of the ‘normal’ silicone sealant and naptha/lighter fluid before painting and it all should stick nicely. 

 

If you don’t have Heptane or would prefer not to use it the other option is to do a thorough degrease of the silicone with acetone IMMEDIATELY before applying the first layer of paint. *In the ‘bad old days’ they used to use the deadly methylene chloride for this; it would swell up the silicones' "pores" and then trap the paint as it "swelled down". It also was a powerful degreaser, could be used to thin the caulk, and also causes death and disability, not to mention the odd birth defect. No longer recommended and hopefully no longer available!!

 

 

Regardless of cleaning, to guarantee success it is always a good idea to applying a thin layer of silicone base mixed with your chosen solvent, and no colour.  This gets stippled on first (use non-latex sponges for this) and allowed to dry thoroughly, preferably overnight. Your subsequent pigmented layers will stick better to this preparatory layer than to the base silicone.

 

 

2. MIXING

Mix your colours in your chosen pigment (oils or silicone pigments) separately onto a lid or in a palette (not into the silicone carrier).

 

 

You can premix some of the silicone base with some of your chosen solvent if you are airbrushing, and store in an airtight container, or you may prefer to mix a little at a time in a small container as you go and use it with your chip brush. Remember that as soon as you expose the silicone to the air it begins to react so don’t make up larger quantities than you can use in a few minutes. Likewise, solvents flash off quickly, which is a desirable quality when applying the paint, but not so great if you get distracted for five minutes and come back to find your solvent/silicone mix is now simply partially gelled silicone!!

 

Load the brush with solvent/silicone mix, pick up a little pigment/paint on the brush and mix it into a puddle on a palette, then flick or spatter it onto the piece.  This way you can test translucency and pull the right amount of colour into the mix.

 

Don't try to mix the right tones right into the silicone or in large batches, or you will waste time and money, because the solvent will flash off before you are ready

WEAR APPROPRIATE PPE!!!

Acetic Acid is corrosive and will irritate your skin, even if you are using a totally non-toxic solvent. If you are airbrushing this goes double- ALL airbrush particles are capable of causing serious lung problems if inhaled, even water, so wear a proper respirator at all times.

 

3. APPLICATION TECHNIQUE:

Your Options are:

·      Spatter using a cut down chip brush.

·      Airbrush

 

Using brushes or sponges to paint directly on the surface can 'muddy' the colours together. It's better to have as little contact with the surface you're painting as possible to avoid lifting colour back off... A gradual build-up of flicked-on translucent shades with a brush or airbrush speckle should give a random natural-looking skin tone. Avoid using thick or heavy layers or you lose all of that lovely silicone translucency.

 

 

You need to work in layers, one colour at a time, letting the previous layer set up before doing the next. It actually takes quite a while to fully cure so avoid doing any abrasive action on the surface, such as using a coarse brush or sponge, with more solvent before completely dry

 

Spatter technique:

The good old spatter technique- exactly the same as you used in kindergarten!! You just cut the bristles down on some cheap brushes and spatter your paint on.

You want quite a translucent paint for this, so that you can barely see any obvious drops on the surface- it is the amount of opaque paint you use which will make something opaque - not the means of applying it.

 

 

Airbrushing:                       

Airbrushes are great, especially for misting and blended, graduated colours. so long as the amount of pigment being applied at any one time is small, then it won't look like blotches of hard colour. Thin the pigments to the point that if you can easily see the colour as it is applied then you have too much pigment in there. It's more arriving at the correct opacity through multiple layers rather than hitting it too hard accidentally with a thick dose of colour.

Airbrush colours need to be thin enough to go through the nozzle anyway, but you could take that same mix you would put through the airbrush and apply it with conventional brushes to get the same coverage.

The art of airbrushing onto silicone is actually to get it to spatter and spit rather than applying a smooth film of colour. If you aren’t already an expert in using your airbrush and manipulating the nozzle to achieve different patterns, then this is probably not the best time to try and learn.

                       

4. COLOUR:

Painting silicone is more like using watercolours than oils, you want layers.

 

Don't try and get one colour that matches skin. Skin isn't a solid tone all the way through. The tint you have put in the silicone when you cast the piece will greatly influence the end result. Have a play with some little test pieces to see what I mean. A very translucent silicone mix will be harder to make look real.

 

Look at your hand- it looks solid, not translucent.

Now think of holding your hand up against a strong light- suddenly it is translucent, and it looks red because of the underlying blood. Yet when we shine a strong light on top of the skin it appears solid again and much paler...

 

So bearing that in mind, the base colour of the silicone should generally be warmer (redder) than your paint job. Also, try mixing your base paint for the first coat with a hint of green IN the mix rather than trying to get a pinky 'flesh' tone- practice by trying to match your own skin, it will surprise you how much green/blue skin actually has in it!! It counteracts the orange and gives a more realistic flesh tone. THEN you go over with what might seem strong colors, but very diluted- blood red, freckle brown, warm yellow, vein blue and green.... All the different colours that can naturally be found in skin. If they are very translucent you get a lovely pointillist three dimensional effect... Same for veining, use what seems a very bright or strong blue-green but dilute it greatly.

 

 

Just remember to wear a mask, safety glasses and gloves when painting- these solvents are strong enough when you’re leaning over the work, let alone when airborne!! .

Here is a basic formula for colour application, just to start you off, (courtesy of Valentina Visintin). The colours are fairly standard paint colours, so even if you don’t have those exact ones you can get a paint chart and figure out the next closest alternative.

 Alizarine crimson or a similar dark blood red colour, with a hint of cerulean blue or sap green added, which will give the skin warmth.

You can sponge this over creases so it sits in the wrinkles, and give a gentle spatter. It should be very weak and translucent –not bright at all.

 

 

A warm tone next, you can use Yellow Ochre with a hint of Burnt Umber. General spatter.

 

Olive green on its own or with a hint of raw umber. General spatter

 

Purple madder with a hint of cerulean blue and sap green. I come back to blush and to increase the reds.

 

Vein tone mixed up with: white, cerulean blue, yellow ochre and a hint of ultramarine blue. Brush on and dab off veins.

 

For blushing, or on older faces, rosacaea, a mix of crimson red and cerulean blue as a blushing.

 

Burnt umber on its own and/or vandyke brown. You can start painting moles or freckles and come back with a super translucent spatter.

 

Add any desired last effect like beard shade (with payne's grey) or increase wrinkles and shadowed areas.

 

Make sure you always use very translucent shades- you can always add more but you cant take it off!! 

 

Don’t apply too heavily or the colour will drip and run before it dries. Likewise, make sure to allow adequate drying time in between layers or you will end up with mud.

 

At the end you may want to airbrush or sponge on a sealing layer of pure solvent mixed with silicone, no pigment. Be very careful not to disturb the paint underneath while doing this.

 

POSSIBLE PROBLEMS YOU MIGHT ENCOUNTER:

 

 

CURING TIME SLOW?

 

If you are finding that the ambient temperature or lack of humidity in your working area is making your paint take ages to dry, there are a couple of things you can do to speed up the cure.

Silicone caulking begins to cure when it comes in contact with moisture in the air. It normally takes about 24 hours to be totally cured, although it will appear touch dry before that. In cooler temperatures or areas of low humidity it can take up to 48 hours. If you live in a very dry climate you may even need a humidifier in the room, or to spritz the surface with water occasionally.

To speed up curing even further, add some glycerine to the mix, as glycerine is hygroscopic (water attracting) and it works like a catalyst.

Some people suggest water, but glycerine will be easier to mix into the caulking. Suggested proportions no more than 4-5pts silicone to 1pt glycerine. If you find the glycerine affects the texture too much, try adding a very small amount of cornflour to reduce the greasiness

 

SILICONE INHIBITION?

 

Occasionally you can have unexpected issues. A piece may be made using exactly the same brand of materials you normally use without issue, but maybe it wont set at all, or it starts out acting like it wasn't going to set, stays pretty tacky for several days, and then finally, reluctantly, sets.                       

The most common issues are when people accidentally thin the caulk too far and it is basically just a layer of paint or pigment with no silicone binding agent which then cannot dry.

           

It can also be something to do with whatever you are using to pigment the caulk. If its oil paint there can be issues between different brands or colours, or an issue with a particular batch inhibiting the mix. It can even be the caulking manufacturer changed the formulation in some way. Brands that worked for years can suddenly stop working for no apparent reason. The only thing we can put it down to is the caulk manufacturers are changing their formulas to make products more eco friendly. Great for the environment, not so great for our silicone painting.  Formulation changes can be frustrating, mainly because there is no mandatory requirement on manufacturers to inform users of changes like this unless such a change alters the MSDS. It's a common problem upstream with raw materials or precursors, and occasionally causes real issues.

           

TACKY SURFACE?

 

You may be diluting the silicone too much- it's easy to end up with mostly white spirits on the brush when you mix the pigment in and end up with a mix of solvent and pigment, which will never dry completely.... If it is a really severe case the only way to permanently fix it is to go over the surface with a layer of silicone and solvent, preferably one as strong as naphtha, and seal in the colour.... Either stipple it on with sponge or use a pump spray to evenly disperse it.

 

SHINY SURFACE?

 

This isn’t a problem per se as much as it is an intrinsic part of the process. It is naturally going to have a bit of a sheen to it unless you have a very textured surface, and if shine does bother you or if you want a particularly matte finish here’s what you do. The idea of "matting" is that silicone always wants to cure as a smooth / shiny surface naturally. The mould you made had texture in it but the paint surface doesn’t have that advantage so you can lose a little detail here and there ... so you te the uncured silicone paint layer so that the final finish is not shiny. Think of this like you would applying a bit of powder to a face to tone down the shine and then do the exact same thing to the painted tacky silicone with a very high quality make-up brush giving a slight dusting to the surface. Some even use actual powdered make-up to do this.

 

Matting silicone:

Your options are:

·      Krylon Brand "Dulling Spray" used on artwork to bring down the shine. Spray a little on, wait a minute or two to dry and... Viola! Instant dulled surface.

·      Bluebird FX matting sealer,

·      Fuse Fx matting powder

·      Icing sugar also works!

 

To use one of the powder options: Dust the whole piece after you have sealed the paint job. Let your silicone paint go tacky and then dust on and pat gently and allow it to finish curing. You want it on the surface, so the finer the powder the finer the matte effect ... you should try this on test pieces first to get the hang and timing of dusting

Timing is crucial, if you do it when it's too wet it can get in to the silicone and make white streaks, leave it too late and it won't work.

Allow to cure overnight, then wash off with water. The fine powder dissolves leaving a matte surface

Another alternative to mattifying agent if you have it in your kit already is a pharmacy-bought brand of "anti chafe gel"-  such as lamasil, or lanacane. Almost identical to an antishine gel, but much cheaper making it good for dummy heads & props. You can also use makeup products like Mac antishine or Kryolan hd primer.

 

Naomi D Lynch (2013) The How and Why of Silicone Part 5 [Online] Available From: http://naomidlynch.com/2013/08/13/the-how-and-why-of-silicone-part-5/ Date Accessed: 11/04/2015