I'm fascinated by the casting process, watching liquid turn to rubber or resin, taking form and turning into a permanent piece of work.
I have put together a slideshow below to show a small selection of the models I have cast over the years in a variety of media, below that is a breakdown of the materials and styles I have worked with.
Most of my resin editions can be ordered in different colours and materials, just use the Contact Kelly page to inquire.
I have put together a slideshow below to show a small selection of the models I have cast over the years in a variety of media, below that is a breakdown of the materials and styles I have worked with.
Most of my resin editions can be ordered in different colours and materials, just use the Contact Kelly page to inquire.
Casting Materials
There is an almost infinite number of casting options, but here's a quick low-down on the types I've experimented with over the years:
IMPORTANT - if using any kind of casting resin, always refer to the manufacturer's guidelines and Health and Safety information.
The following is purely an example of my own experience documented to my best knowledge, I cannot guarantee it's accuracy.
White Resin
Polyurethane Resin during curing
This is the most common material used for casting model horses. There are two types of resin commonly used in the production of model horses; Polyurethane (PU) and Polyester (PE)
PU resin is most commonly used for Model Horses, it has some flex to it making it more suitable for casting models with small fragile bits like legs and ears. It does have a tendency to warp under pressure so many casting companies reinforce the legs and tails of their models with a metal wire or pin. PU is usually either white or cream in colour but will normally yellow when exposed to UV (sunlight).
PU resin is a two-part mix. It is supplied as a Part A and Part B, which are mixed in equal measures. Part A and Part B are both clear, but you can just about see that one has a slight straw-colour to it and the other is very slightly thicker in consistency. Once mixed, the resin remains liquid for a time from 30 seconds to about an hour depending on which grade it is. I use mostly 300 grade, which remains liquid for about 1.5 minutes which is just enough time to mix, pour, vacuum and remove surface bubbles before the reaction takes place. Unlike the gelling action of PE, PU resin has a tipping point that takes it from liquid to solid very quickly; when casting a medallion you can watch the clear resin "bloom" and turn to a solid white resin in a matter of seconds. During curing the resin gets extremely hotSmall details and thinner areas cure SLOWER than thicker areas, which is the opposite of what you might expect and means that knowing when a model is cured enough to de-mold becomes more instinctive than scientific, as they look finished much sooner than they actually are.
PE resin is a transparent straw colour and is usually pigmented or filled with a powder made from ground marble (white) or slate (black). PE has a very distinctive smell to it; it is also used in the manufacture of boats, cars and baths when with fibreglass for a super-strong shell. It isn't used a great deal in the manufacture of Model Horses though, as although it is very strong and rarely warps, it can be brittle without the added fibreglass content.
PE resin uses a catalyst to cure; the catalyst is very volatile, flammable and corrosive (another reason many casters avoid PE). You add a few drops of catalyst to the resin to begin the curing process. The resin remains liquid for about 10 minutes (depending on grade) until it begins to gel. The gel-point is the point at which you can no longer pour, vacuum or touch the resin. Once the gel-point is passed, the resin gradually hardens. As this is a chemical reaction the resin will get very hot whilst curing!
Both PE and PU resins can be bought in various "grades". Smooth-On white resins are graded on the length of time they remain liquid after mixing before they cure (set), they are also available in various hardness grades, but generally all model horses are cast in the 300 series which is Smooth-On's standard, white resin.
PU resin is most commonly used for Model Horses, it has some flex to it making it more suitable for casting models with small fragile bits like legs and ears. It does have a tendency to warp under pressure so many casting companies reinforce the legs and tails of their models with a metal wire or pin. PU is usually either white or cream in colour but will normally yellow when exposed to UV (sunlight).
PU resin is a two-part mix. It is supplied as a Part A and Part B, which are mixed in equal measures. Part A and Part B are both clear, but you can just about see that one has a slight straw-colour to it and the other is very slightly thicker in consistency. Once mixed, the resin remains liquid for a time from 30 seconds to about an hour depending on which grade it is. I use mostly 300 grade, which remains liquid for about 1.5 minutes which is just enough time to mix, pour, vacuum and remove surface bubbles before the reaction takes place. Unlike the gelling action of PE, PU resin has a tipping point that takes it from liquid to solid very quickly; when casting a medallion you can watch the clear resin "bloom" and turn to a solid white resin in a matter of seconds. During curing the resin gets extremely hotSmall details and thinner areas cure SLOWER than thicker areas, which is the opposite of what you might expect and means that knowing when a model is cured enough to de-mold becomes more instinctive than scientific, as they look finished much sooner than they actually are.
PE resin is a transparent straw colour and is usually pigmented or filled with a powder made from ground marble (white) or slate (black). PE has a very distinctive smell to it; it is also used in the manufacture of boats, cars and baths when with fibreglass for a super-strong shell. It isn't used a great deal in the manufacture of Model Horses though, as although it is very strong and rarely warps, it can be brittle without the added fibreglass content.
PE resin uses a catalyst to cure; the catalyst is very volatile, flammable and corrosive (another reason many casters avoid PE). You add a few drops of catalyst to the resin to begin the curing process. The resin remains liquid for about 10 minutes (depending on grade) until it begins to gel. The gel-point is the point at which you can no longer pour, vacuum or touch the resin. Once the gel-point is passed, the resin gradually hardens. As this is a chemical reaction the resin will get very hot whilst curing!
Both PE and PU resins can be bought in various "grades". Smooth-On white resins are graded on the length of time they remain liquid after mixing before they cure (set), they are also available in various hardness grades, but generally all model horses are cast in the 300 series which is Smooth-On's standard, white resin.
Clear Resin
Clear, or Water-Clear resin is often used for "encapsulation"; the process of casting a block of resin containing an interesting object such as a flower, or in a more functional way such as a circuit board (to prevent moisture from damaging the connections), but it is occasionally used in the Model Horse world to create unusual models of interest.
PU Clear resin is restricted as it carries higher Health and Safety risks than it's white counterpart. However, it is a much more reliable casting resin than the clear PE and sets to a fully hard state in a reasonable amount of time whereas PE clear resin can take weeks to full harden. Additives are used to protect this type of resin from yellowing in sunlight and pigments can be used to colour it, however for coloured models colour-neutral resin is a better choice as water-clear resin is sold at a premium. Clear resin takes much longer to yellow under UV light, so is a good choice for models that are to be displayed outside or in direct sunlight, it can be pigmented white to mimic "normal" white resin whilst keeping the strong UV resistance.
PE clear resin has the same distinctive smell as normal PE resin, when poured it is a pale blue/green colour which, once mixed clears to leave a pure, water-clear casting. In my experience I have found it tricky to make PE clear resin cure fully, some casts can take weeks to fully harden and lose their tacky feel, unfortunately taking such a long time to harden means that dust can stick to the surface and fingerprints are almost inevitable. Once fully hard though, PE clear resin can be sanded and polished to give a perfect, glass-smooth finish.
Clear resin can be pigmented, but as it often carries a much higher price than white resin or the colour-neutral resin (see below), it is usually only used when a pure water-clear model is required.
PU Clear resin is restricted as it carries higher Health and Safety risks than it's white counterpart. However, it is a much more reliable casting resin than the clear PE and sets to a fully hard state in a reasonable amount of time whereas PE clear resin can take weeks to full harden. Additives are used to protect this type of resin from yellowing in sunlight and pigments can be used to colour it, however for coloured models colour-neutral resin is a better choice as water-clear resin is sold at a premium. Clear resin takes much longer to yellow under UV light, so is a good choice for models that are to be displayed outside or in direct sunlight, it can be pigmented white to mimic "normal" white resin whilst keeping the strong UV resistance.
PE clear resin has the same distinctive smell as normal PE resin, when poured it is a pale blue/green colour which, once mixed clears to leave a pure, water-clear casting. In my experience I have found it tricky to make PE clear resin cure fully, some casts can take weeks to fully harden and lose their tacky feel, unfortunately taking such a long time to harden means that dust can stick to the surface and fingerprints are almost inevitable. Once fully hard though, PE clear resin can be sanded and polished to give a perfect, glass-smooth finish.
Clear resin can be pigmented, but as it often carries a much higher price than white resin or the colour-neutral resin (see below), it is usually only used when a pure water-clear model is required.
Colour-Neutral Resin
Colour Neutral resin is the resin used when a specific colour or filler is required. It is a pale straw colour when supplied and if cast alone produces pale straw coloured models, however when a pigment or material is added, it adopts that colour truly.
I use this type of resin to produce "Wine Gum" style models such as the yellow and orange medallions on the bottom row of the photo shown; to produce sparkly or filled models, such as the gold, antique gold and pearl gold models on the top row of the photo and for cold-cast metals such as bronze, aluminium, copper or other metals (not shown).
I use this type of resin to produce "Wine Gum" style models such as the yellow and orange medallions on the bottom row of the photo shown; to produce sparkly or filled models, such as the gold, antique gold and pearl gold models on the top row of the photo and for cold-cast metals such as bronze, aluminium, copper or other metals (not shown).
Cold Cast Metals
Cold Cast metal models are made using Colour-Neutral resin mixed with real metal powder. There are several ways of producing cold-cast metal models:
1. The resin is "filled" with a very fine powdered metal, poured into the mold, allowed to set and then once fully cured it is cut back using a fine wire wool* to reveal and polish the metal. This method is the most expensive, but gives the models a good weight and a nice cold feel, the closest feel you can get to a hot-foundered metal model.
2. A small amount of resin/metal mix is poured into the mold, then the mold is rotated until the resin cures, giving a "shell" of cold cast metal. The hollow is then poured with normal resin, usually pigmented black. The model is lightly polished to reveal the metal. These models are light in weight but have a cool feel to the surface, although sometimes the resin used to pour into the hollow is filled using iron, a cheap metal that is very heavy, this gives the model the weight you would expect from a metal model.
3: The mold is dusted with a metal powder. Black pigmented resin is then poured into the mold. On demolding, the model is lightly polished to give the effect of aged metal. These models look very nice but are not cool to the touch and are generally as light as normal resin.
(*never use normal wire wool on a cold-cast metal model, use only grade 0000 as this will not scratch the finish but will reveal the metal and make it shine)
Cold Cast metal models "age" just as foundry cast models do, they can also be treated with patinas and acids to give effects such as ageing, rust or verdigris, as illustrated by the model shown below, which is a cold-cast copper model treated with acid and then sealed:
1. The resin is "filled" with a very fine powdered metal, poured into the mold, allowed to set and then once fully cured it is cut back using a fine wire wool* to reveal and polish the metal. This method is the most expensive, but gives the models a good weight and a nice cold feel, the closest feel you can get to a hot-foundered metal model.
2. A small amount of resin/metal mix is poured into the mold, then the mold is rotated until the resin cures, giving a "shell" of cold cast metal. The hollow is then poured with normal resin, usually pigmented black. The model is lightly polished to reveal the metal. These models are light in weight but have a cool feel to the surface, although sometimes the resin used to pour into the hollow is filled using iron, a cheap metal that is very heavy, this gives the model the weight you would expect from a metal model.
3: The mold is dusted with a metal powder. Black pigmented resin is then poured into the mold. On demolding, the model is lightly polished to give the effect of aged metal. These models look very nice but are not cool to the touch and are generally as light as normal resin.
(*never use normal wire wool on a cold-cast metal model, use only grade 0000 as this will not scratch the finish but will reveal the metal and make it shine)
Cold Cast metal models "age" just as foundry cast models do, they can also be treated with patinas and acids to give effects such as ageing, rust or verdigris, as illustrated by the model shown below, which is a cold-cast copper model treated with acid and then sealed:
