How to build a resin kit !
One of the biggest mysteries that is out there in the modeling
community is how to Prep, paint and build a resin kit. I've
recently built a number of them for different clients, and finally
decided to document the step by step process. I'll do my best
to explain each step as I go along, but bear in mind, everybody
will and can do it different. By no means do I declare myself an
expert! I'm just a 'not small' man hanging out in the back room
with a knife and determination!
First you clean!
The real key and difference to doing a resin kit from normal type plastic or die cast kits is the preparation. When a resin piece is cast, the liquid mix is poured into a mold, which is usually covered in some sort of mold release. What kind will vary from different manufacturer, but needless to say you need to make sure you're piece is clean. Now sometimes I'll clean a cab after I've done all the sanding and drilling I'm going to do, but regardless, this must be done before the first prime coat. There are a couple of different ways to do it. One method is using lacquer thinner. Dip the piece into a jar of the stuff, leave it there only for a few seconds, take it out and dry it off using a cotton rag of your choice. DO NOT leave the piece sitting there for longer than a minute or so at the outside. The lacquer thinner is excellent for turning your piece into a blob of melted goo! My preferred cleaner is 'Westleys' Bleche White' a tire cleaner you can find at most auto parts stores. It's less caustic than the lacquer thinner, so you can set the pieces into a bowl of the stuff, and gently scrub it with an old toothbrush. After either method, wash the parts in warm soapy water..and rinse really well to remove any soapy residue. Now you're ready to work the piece over.
Prep for parts!
This next stage is really where you get to start having some fun. This is where you can avoid lots of hassle by planning ahead. What I like to do first is completely go over the piece with a set of needle files and sanding sponge. When a kit is poured, or shot into a die like styrene, there are small sharp edges and thin extra material that squeezes out of the edges of the actual piece itself. This is called flash, and it needs to go away! I usually cut away with a knife blade first, and then carefully sand all the edges square and clean. Pay particular attention to the windows, and bottom edges of the cab, fenders etc. The front of the TLC Peterbilt 379 kits have a small raised bump on the front leading edge of each that go fit around the grills that come with liberty classic or Spec cast Pete parts. I don't like them, so I sand them off as well.
Once you've gone over the basic piece, line up ALL the parts you want to have on the finished rig. Make sure that each part fits where you want it easily. This is often referred to as 'dry fitting'. Drill all the holes for any extra lights on top, and the mirrors. These kits don't come with the peep window on the passenger side door. I draw a small rectangle with a pencil where I want it to go, and then using a drill bit, make a hole at the top of the rectangle, and at the lower end. Then, carefully work a knife down each side to connect the two circles, and BAM...small oval window. I also like to shave the visor back so the new stainless version fits flush how I want it...either straight out or dropped. Once you're satisfied, look it over really well again, then get ready to paint.
Shake, rattle and roll!
Painting is always a task people seem to be afraid of. Don't be, it's not rocket science. It just takes some practice and patience. The first thing I do right before painting is wipe the piece down with Isopropyl Alchohol (rubbing alcohol.) This removes all the grit, grime and oils put on their by your fingers. Then, I take a set of locking forceps and grab the the front support for the grill...anywhere that isn't going to be seen once you're finished. I'm a big believer in auto paint. Not enamel, but lacquer based, like the little type cans you see in auto part stores. I make sure and buy the same brand primer (sandable), color coat, and top clear coat. Brands vary, but the more common are Dupli-Color or Plasti-Kote. Now that you've got all the paint you're going to need, go outside where its ventilated.
First, prime coat. I do one fairly solid coat to start. This really shows what voids or deformities are in the cab. Let the primer dry and then fill the holes or voids with your putty of choice. Some people use auto bondo, I like to use modelers putty, called Squadron White Putty. Regardless, fill in small amounts until the hole is filled, and sand lightly until flush. Now blow it off, and prime again. If after dry, the piece looks good, you're ready to color coat. There are a few different ways to do it, but I like to flood coat it. In short, you start beyond the piece, spray and move the paint across the piece, not stopping until you're past it. Heres' where the practice comes in. You want enough to have a good even glossy coat, but not too much so it runs. Let it dry, and do another coat. Finally, if all still is on track, top coat with at least once coat of the clear. This is just a basic article, so I'm not going to go into all the methods for two or three tone paint jobs. I'll save that for a later date.
Below are some thumbnails that show each stage of the work on this particular cab. The first picture shows all the parts and pieces, and some of the tools I use before I begin. The second shows the cab before any of the prep work has been done. Note the flashing in the sleeper door that has to be removed. The third shot is after I've done all the sanding and filling, before sanding the filler. The last shot shows the cab ready to assemble.
My friend Jim, who lived just down the road from me for a few years, wrote a nice write up on resin kits so I thought I would share it here. He is an awesome talented designer and builder and painter whom I learned a lot from. I suggest you take a look around his webpage and send any of your friends who are interested in his models his way.
E James Small (Jim )
Space 1999 and Sci_fi etc models builder and designer.
Welcome to the world of Resin Kit Building!
If you are already familiar with making resin and composite model kits, you can ignore this piece of paper. However, if you are new to the hobby, and are only familiar with building the commercial injection molded styrene models that have been the mainstay for so many years, you may find some tips here that will help you to get the most out of your new kit.
The model kit you have just purchased and others like it are generally referred to as “Garage Kits”. This term has been coined to represent the fringe of the model kit manufacturing community (generally individuals) who produce kits (yes, sometimes in their garage!) that number in hundreds or dozens, rather than the hundreds of thousands or millions that constitute the bulk of consumer-oriented commercial model kits. These Garage kits may, at first glance, seem terribly crude compared to the mainstream kits you may be more familiar with. The reason for this is simple. Garage Kit manufacturers are rather low key and do not have a lot of money at their disposal for a machine shop to produce expensive steel molds (commercial kit molds can cost up to half a million dollars to produce) and the other multi-million dollar equipment and staff used to produce mass market kits on a very large scale. Instead, Garage Kit manufacturers use silicon rubber molds and urethane resin to produce the parts for the kits like the one you have in front of you now. This process allows for lower startup costs than the injection molded production runs the big companies use, but it also allows Garage Kit manufacturers to produce more specialized products with much smaller production runs that would be impractical for the mainstream companies. This is a good thing, because it allows the enthusiast to buy kits that would not normally be available if left up to the usual large manufacturers. Yes, the Garage Kits are rather expensive part-for-part when compared to the mass produced ones available at department stores, but that’s the price paid for having a kit available that’s more suitable for your particular interest. Also, Garage kits are more labour intensive on an individual basis, and the materials are more expensive per kit as well when compared to the mass-produced examples.
YOUR KIT BEGAN WITH AN IDEA First, the model your kit is based on was extensively researched to the point where an accurate master pattern of the model could be made. This master pattern was built completely by hand, keeping in mind that the law of gravity and physics of fluids would play a part, and a rubber mold of this master would have to be made. The completed pattern was then covered in a silicone rubber compound, which begins as a thick gooey liquid that, when a catalyst is added, hardens around the master. After about a day, the flexible rubber mold was then removed from the pattern and casting of the resin copies were then made from urethane resin. Urethane resin is a two part liquid that, when combined, reacts to form a solid compound. The mold was prepared, then a quantity of resin was mixed and poured into the mold. Within a few minutes, the copy of the master becomes solid, and can be removed. The resulting pieces are the parts of the model you now possess. All of this is done by hand, one piece at a time, making the production run fairly labour intensive and time consuming. This process replicates very accurately the original master model down to the last detail, but the casting process usually introduces some flaws, such as air bubbles, “flash” and spillover along the mold separation lines or edges. Sometimes some excess resin has “heaped” at the top of the mold where it was poured. You must sand this flash before the parts can be assembled into the final unit.
KIT PARTS PREPARATION As a consumer, you will have to pay more attention to the preparation of the parts with a Garage Kit than you would an injection kit. There are flaws that you will have to fill, trim and sand before you begin the assembly of the kit. Trimming some of the “positive” bubbles is easy. Usually they can be picked out with the end of a knife. To fill “negative” bubbles, you can use standard modeling or automotive putty, or better yet, use medium grade cyanoacrylate, or “CA” (superglue) and a little accelerator. Cyanoacrylate is the “official” name given to what you would normally call superglue. First, apply a bit of accelerator to the inside of the bubble, allow to dry then apply a drop of CA to fill the cavity, Then more accelerator if necessary. For some problem areas, you can apply the CA like this in layers to build up the surfaces. When hardened, the superglue sands pretty much like the resin the kit is made of. Use a small file to remove most of the material and then finish with fine sandpaper.
ASSEMBLING YOUR KIT Assembly of the resin parts of your kit is best done with CA adhesives. I recommend the better quality CA that can be purchased at your local hobby shop. There are three different grades you should know about. The thick grade CA flows much like corn syrup, and can be used for areas where large gap filling is required and quick setting is not necessary. The medium grade is the most useful. It fills tiny gaps and is just runny enough to use a bit of capillary action to inch into not-so-deep crevices. The thin grade runs like water, and can actually be dangerous if you are not careful (never squeeze the bottle while looking into the spout, for example or you will do some very serious damage to your eyes!). This thin CA will bond your skin instantly. Exercise EXTREME caution when using this stuff! Use the thin CA by holding the parts to be joined together, and then apply a TINY amount of thin CA to the joint. Capillary action will carry the glue into the joint, forming a very solid bond. It is important that you make the parts match very closely. The thin CA will not fill any gaps.You will also find the use of CA Accelerator (also available at your hobby dealer) very useful. Sometimes when a joint is stubborn and will not seem to bond, you can force the glue to cure instantly by giving it a shot of accelerator. This also helps in gap filling.
Safety tip: The use of accelerator will cause the glue to cure VERY quickly, and a lot of heat is generated. If you have any of the glue on your skin which is hit by the accelerator, it will cause very nasty burns (especially with the thin CA). Keep away from the fumes generated. Always exercise caution when using CA and accelerator to avoid some very unpleasant adventures! Remember, we want model building to be FUN! Finishing and painting your model is just like the styrene kits, with one major exception. The resin your kit is made from will take whatever kind of paint you want to lay over it. It will even accept automotive lacquers (which damage styrene kits) quite happily! Use the standard preparation techniques for all models, like washing the parts to eliminate greasy fingerprints and mold release agents, that you would use with the Styrene kits. I also recommend priming all the parts before painting with an cellulose or laquer based primer, like automotive primer. This also helps you locate minute flaws before finishing.
CONCLUSION The assembly and preparation techniques of your kit may seem very difficult to you initially, but in reality, once you understand the construction techniques and nuances of doing these kits, you may never want to build a styrene commercial kit again!
My friend Naz , aka Steve Nasburg, wrote a resin prep tutorial which I thought I would also share.