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How To Construct Resin Kits

Considering how many companies use resing these days, it is surprising how little information there actually is on the web regarding how to build a model of this material. The following "how-to" is a little something put together from information gleaned at various sites on the web, and amended to cater for 1:56th/1:60th scale resin wargame vehicles.

Resin is used as the primary material for many wargames models for several reasons. Since most wargames companies are small, and do not have access to the sophisticated (i.e. expensive) injection moulding presses, alternatives are a must. Since a resin model is cast into an open-topped rubber mould as a liquid that eventually hardens, it does not require extensive facilities. Because the moulds are soft and flexible, the individual parts can be more complex, thus reducing the number of individual parts required- a bonus for the average wargamer who wants a kit that is easy to complete and looks good. Once it is set, resin "holds" detail really well, and most kits have extremely many fine details hidden everywhere about them. The SdKfz 251 now sold by KHI, made by Tony Ashcroft of NZWM, is a perfect example. Once it is assembled, you think you've seen all the bits that need work, After undercoating, you suddenly spot a few more bits, and once you've actually started painting it, even more detail jumps out at you. This little kit is really amazing.
Resin kits are not built in quite the same way as commercial injection-moulded plastic kits. Resin has its own little quirks (for that matter, each brand of resin is individual). It can be hard to build properly, and, due to the hardness of resin, special techniques are sometimes required. None of them are too difficult to master, though.

Required Tools

Obviously, you will need some tools to assemble the model properly. Assembling a tool box is a very individual undertaking - some modelers swear by tools that you find useless, but the following is a listing of some of the basic items (as well as some optional ones) you will need in order to assemble a basic resin model. Many modellers and gamers will have most of them already. Since they will, if looked after properly, usually last for a long time, any expense is actually pretty limited.

A sample work-desk and some tools
Insert picture of Desk and Tools here.

Setting up the Work-area

If you do not have access to a workbench, you should get a flat, smooth board about two feet long and one-and-a-half feet wide. An MDF or hard wood plank will do just fine.
Your work area should always be kept tidy, clean, and well-organized. It is vital that it be well lit; the best light source is the sun. If a window is not available, make sure that you have plenty of good illumination that is comfortable to your eyes.
Modeling tools can be kept in drawers or old kit boxes, but it is better to have a dedicated toolbox.


I suppose a quick safety chat would not go amiss at this point. It is important to remember that any tool capable of cutting through plastic and metal is doubly capable of cutting through flesh! I've lost track of the number of times I "forgot" this important bit of advice and cut myself.
When using a cutting tool, make sure you cut away from yourself to avoid accidents. A blunt blade will be harder to control and require more pressure to cut, increasing the chances of slipping and causing injuries, so be sure that your blades are as sharp as possible at all times.
Most of the glues and paints we use, as well as the resin dust itself, are toxic to some degree. Avoid breathing the fumes as much as possible, and be sure to work in a well-ventilated area.

First Steps

First and most importantly, read all of the instructions thoroughly before you start cutting or glueing anything. Lay all the parts out on a clean flat surface and make sure all the parts are there. It may sound obvious, but it is very easy to get carried away and start assembling a model without checking. A missing piece will then stop you from finishing it (which is far more annoying than finding that a piece is missing before you start). At the same time, check if any parts have been damaged during transit. Damage usually takes the form of chipping, which can be fixed with little trouble. Compare any drawings or photos you have to what you are building.

An unassembled kit, seen exactly as received
Unassembled kit, as delivered

In some cases, if the missing or damaged part is large or important, it may be necessary for the kit to be returned, and this will be much easier to do if the kit hasn't been started.


The next step is to start preparing the kit for assembly. As this is a multi-stage process, which I'll go through step by step.

1. Washing

Clean the parts thoroughly with a mild soap in lukewarm water. The reason for doing this is to make sure all traces of mould release fluids are removed. It also gives a very slight abrasion to the surface of the model that will help with paint adhesion. Use a sponge or soft brush. Be careful not to damage or break off any cast-on detail parts. I usually leave the components to soak for a little while before scrubbing, and again for a little while after. Then remove the models, rinse thoroughly and allow them to dry.
This isn't always necessary but I find it's generally better to be safe than sorry, especially as it will be that much more difficult to do once you have assembled the kit and begun painting it!

2. Removing the parts from the Sprues

Just like with metal and plastic models, there will be excess material that needs to be removed from the parts of the kit before you can assemble it. The main difference is that, with resin models, the bits needing removal can be larger and must be removed with more care. These are the result of the casting process and unavoidable but all can be easily dealt with.
The mould plug is the area where the resin is poured into the mould. This is the biggest piece of excess resin. A mould plug can appear in many different shapes, depending on the shape of the model. The most common are V shapes that are on the side of a detailed or odd shaped component or a large rectangle going onto a squared component. These will need removing and may take some effort with a larger part.

One kind of mould-plug
Bottom of unassembled kit, showing mould plug

One kind of mould-plug
Bottom of unassembled kit, showing mould plug

Check your instructions and references again to be sure that the items you see are actually mould plugs and not part of the kit. To remove the larger parts from the mould plug, especially when it is too large to use clippers easily, cut them off with a saw. Unlike with clippers, this can be done as close to the model as you like. It's usually best to do it slightly away from the join though just to make sure that any deviation in your cutting line doesn't affect the model. Again after the mould plug has been removed, use a file to ensure a smooth finish to the surface.
With smaller components, a pair of clippers and a file should suffice. Don't twist the parts off the wafers or sprues - this is the best way to damage them. With your clippers remove the mould plug at a point above where it joins the component. Don't use the clippers next to the actual part. This is because clippers are quite a crude tool and often damage the areas on either side of where you cut. After clipping most of it away use a file to remove the last of the mould plug and to ensure a smooth finish.
Be careful not to apply too much pressure- resin is brittle.

3. Removing Flash

Resin pieces are produced from rubber moulds that sometimes have a split line. Flash is formed in one of two ways. The first way flash is formed is when it leaks slightly between the two layers of the mould. This leaves a thin membrane that usually fans out from the component. Consequently there will often be a line on the model that shows where the mould joined. Sometimes these are fine enough that they can be ignored. To get the best results, however, they will need removing so that they don't show up after painting.
The second way that flash is formed is deliberate. Thin gaps in the mould allow resin to flow into other parts in the mould without filling a gap. For example, when making a cockpit canopy or a window, large gaps are needed between the frame of the windows. In order to allow that gap, the mould only needs a very small gap for the resin to flow through. This leaves a thin membrane between the larger parts of the component.
Check your instructions and references again to be sure that the items you see are actually flash and not part of the kit. To remove these lines, use a modelling knife, file or sandpaper and carefully scrape or file away the line. This shouldn't take too long and makes a big difference to the finished model. Repeat this process for each part, paying special attention to small detail pieces.

Again: be careful not to apply too much pressure- resin is brittle.


So, now we reach the point where we actually begin assembly.


You will need either cyano-acrylate (CA) glue or two-part epoxy glue to assemble your model. CA glue, also known as superglue, bonds just about anything very strongly (including skin), but the bonds formed are weak unless the mating surfaces are clean, absolutely dry and fit well. Superglue is best applied with a small toothpick. The better the fit between the parts to be joined, the stronger the bond. Be extremely careful when working with superglue glue. It contains some minute quantity of cyanide, which is a toxic compound. Use it in a well-ventilated area and don't breathe the fumes. Never, ever heat it to make it cure faster.
The term epoxy glue covers a variety of adhesive resins that are cured by a chemical reaction instead of evaporation. Most epoxies come as a two-part set that must be mixed in equal proportions, yielding a strong and nearly universal glue. They require a few minutes to set, making them perfect for assembling variable position parts.


Once the components have been washed and all excess resin has been removed, the kit should be ready for assembly. If the model has any interior detail, now might be the best time to paint it, as it could be difficult once the model is assembled.


Before gluing the components together, it is a good idea to dry fit them. This just means placing the parts together to make sure they fit okay. This is useful, as it will point out any potential problems such as uneven joins and slight gaps in the joins. Unfortunately gaps are unavoidable with some joins. If there is an uneven join just quickly take a file to it and make it flat before gluing.

A dry-run (test fitting)
Kit Parts Being Test-Fitted

Warped Parts

Warpage can easily occur with thin components as thin resin components are susceptible to temperature just after casting. To get a warped piece into the right shape (or even to just reshape a piece like a piece of track) just immerse it in hot water and gently bend it. With a larger piece it is best to do this in stages. Bend it a little, allow it to settle and repeat until it is in the correct shape. Larger pieces may also require longer immersion to soften. If you don't want to use hot water then a hair dryer should give the same results, just don't let the piece get too hot (or blow away!). Do not heat resin with any kind of flame.

Assembling the Resin Parts

Glue the parts together according to the instruction sheet. Glue the components together straight- don't worry if there is an occasional gap, those can be taken care of in the next stage. It may be an idea to leave off some of the more fragile parts until after you have painted the main assembly. If this is the case, make sure the joint won't be too apparent afterward, since you won't be able to apply putty on the painted surfaces.

An all-resin kit
Assembled resin-only (OK, I cheated- I placed the MG stand and tools on the fenders already)

Assembling the Metal Parts

Your kit may include some metal parts. Metal requires the use of either superglue or epoxy glue for assembly. Start by cleaning all the parts, removing flash and mold lines. Assemble the parts without glue to see how they fit together. Cut, file and bend where necessary to improve the fit. Some parts may be left off for painting to make the job easier. If this is the case, make sure the joint won't be too apparent afterward, since you won't be able to apply putty on the painted surfaces.

A resin-and-metal kit
Assembled metal parts

A resin-and-metal kit
Completely assembled resin and metal kit

Gaps and Putty

Occasionally there may be gaps where parts meet, or where a small bubble (void) is present in the resin. It's best to glue all your components that will need filling at the same time as it will save you time and putty.
Putty is a malleable substance that hardens when it dries. Putty comes in small, squeezable tubes, and several brands are available at your local hobby store.
Mix the putty per the instructions. Apply the putty with a toothpick - just enough to fill the gap - and let it dry before sanding off the excess. Model putty takes forever to dry when applied in thick coats.

An assembled kit, showing areas filled with putty
Insert picture of Assembled Kit Showing Putty here.

The structural strength of regular model putty is somewhat poor. If you have to build up a large area, two-part epoxy putty is a better choice. Epoxy putty consist of two bars of different colors that must be mixed in equal proportions. The putty will adhere to almost any surface, so work it with damp tools. Always wash your hands and your tools immediately afterwards.
If the gap to be filled is in a detail-dense area of the model, apply strips of masking tape on either sides of the gap to prevent the putty from filling-in the detail. Remove the tape once sanding is done. You could also work the putty with sculpting tools, blending it into the model.
Once the putty has set it should be sanded and blended into the resin parts.

Finishing Assembly

Once the entire model is assembled, apart from the odd little bits that have been left off to simplify the painting process, we need to wash and rinse the whole model again, in order to remove any oils left by our fingers and whatever tools we have used.

A completed kit
Insert picture of a Completed Kit here.


Priming the model with a car-body primer, available from most motor stores. Most model primers don't have the required solvent strength to adhere to resin properly. If the primer comes away, then anything you have painted over it comes away too, which would be a bad thing! I also won't go into the debate about what colour primer to use- each to his own. I've seen (and even tried, in some cases) black, grey, brown and white being used. I personally prefer grey (or sometimes white), simply because it doesn't deaden the colours I paint onto it, and the fact that black tends to hide the detail (to my eyes, anyway) and makes it more difficult to paint the model.

A completed, undercoated kit
Insert picture of Undercoated Kit here.

When you've reached this stage, it's simply a case of choosing your colour schemes and painting your model!

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