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.
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.
Insert picture of Desk and Tools here.
- Dust Mask When filing or sanding resin components, it is usually a good idea to wear a face mask. Like any fine dust, breathing resin dust is not particularly good for you. These masks can be cheaply bought from most hardware stores- a simple gauze mask with rubber-band straps to hold it in place are the minimum requirement.
- Hobby Knife Recent governmental legislation in some parts of the world has made it increasingly difficult to obtain good craft knives, but nonetheless you are going to need one. This is usually a handle with interchangable blades. Scalpels and models with retractable blades are also available. Get one with a fine handle and one with a heavier handle. They are available with all kinds of plastic, metal or rubber handles. Pick one that feels comfortable in your hand. If you only buy one tool, make it a good knife - it will be necessary for cleaning up castings prior to assembly.
- Glue There are many different types of glue. In order to work with resin kits, you can use only normal modelling glue, although this is not really a worthwhile option as it wont bond properly, so teh parts will eventually fall off. Ideally, you will have different glues for different kit materials. Buy some cyano-acrylate "super-glue" - both the thin quick-setting and the thicker gap filling types. For working with wood parts and also for the eventual basing (if you base them), get some white glue. For some resin kits, a two-part epoxy might be necessary.
- Files and Sandpaper (medium, fine and extra-fine) After a knife, a set of files is the most useful part of your tool kit. They are used for cleaning and smoothing castings and filing pieces 'to fit' where necessary (a neccessary step due to the nature of resin castings). Files come with several different profiles: flat, round, half-round, and several other shapes. These can be worked in tighter areas than sandpaper and will be easier to work around cast surface details. It is a good idea to have as wide a selection as you can afford. Sandpaper or sanding pads (I use my wife's disposable nail-files!) are also useful for sanding larger areas, or getting a straight finish over a larger area. Purchase a selection of papers from 220 to 600 grit. Also, some cheap hardware store coarse grit for taking down large lumps of casting flash is useful, but be careful not to damage the model's finish.
- Saws There are many types of saws. Probably the best for working with a resin kit is a jeweller's saw or, if you can't get one, a razor saw. A jeweller's saw gives very fine cuts but the blades are quite fragile. A razor saw is more substantial but won't give as fine a cut. Something else that has also become a lot more common these days is a photo-etch saw-blade that fits onto a standard scalpel handle.
- Pin Vise and Drill Bits You will need one of these if you want to drill holes in your components. This is usually only necessary if you want to add strength to a join with large and/or heavy components by pinning them with metal rod, or if you wish to hollow out openings or gun-barrels on solid resin castings.
- Clippers Clippers are useful for removing pieces of plastic,metal or resin that are too large to safely remove with a knife. They are also faster and easier to use than a saw so make a good middle ground tool. Start with a sprue nipper and a fine pair of scissors. Get a few types that are well made and they should last a long time.
- Tweezers These are great for picking up and holding small parts, and (for some of us!) necessary for placing decals exactly where you want them. Get at least one pair of extra fine needle pointed tweezers.
- Clamps Clamps are very useful for holding parts together while the glue dries, as well as to hold parts in a specific position while they are being worked on. In a pinch, clothespegs will work.
- Pliers Pliers come in handy when you need to hold small parts so that you can work on another section of that part. The most useful ones are "needle-nose" pliers.
- Toothpicks These come in handy when you need to make small wedges, or to hold small parts while painting them, or to apply small amounts of glue...
- Paintbrushes Get a varied selection. Purchase some inexpensive brushes for broad coverage and for applying washes. These are also good for setting decals. Don't skimp on good brushes for detail work or your finish will suffer.
- Variable Speed Rotary Tool such as Dremel, Minicraft and similar This can be used any time you need to sand, file or cut something and will greatly increase the speed of those tasks. It is, however, a tool for the experienced modeller and should be used with care.
- Airbrush Many of us still paint by hand, using brushes, but an airbrush makes getting a neat sprayed-on camo-scheme much easier.
Insert picture of Mask here.
Insert picture of Knife and Files here.
Useful extra items:
And for the richer among us:
Insert picture of Dremel here.
Better tools usually result in better finishes.
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 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.
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.
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.
Bottom of unassembled kit, showing 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.
Kit Parts Being Test-Fitted
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.
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.
Assembled metal parts
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.
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.
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.
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.
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!