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Resin is a plastic like substance, and well cast resin parts may be hard to tell apart from plastic. Resin starts out as two different chemicals, and when combined they solidfy. It is very similar to a two part epoxy which you may have used (JB Weld, 5 minute epoxy etc). When in the liquid state resin can be poured into a silicone mold to form a part. Resin is used by aftermarket suppliers because it is relatively cheap to work with compared to styrene plastic which requires very expensive machines (hundreds of dollars vs millions of dollars to get started).
There are a couple of different ways you can buy finished resin.
Parts - resin may be used to make custom parts like wheels, motors, a modified hood etc. This is the easiest and least expensive way to see what resin is all about, because you are just adding something or swapping the resin parts for kit parts.
Body - This will require a plastic model to finish, often a very specific kit. This is usually done to provide a slightly differant body style from that offered in a kit, like going from a hardtop to a convertable, or from a stock body to a custom body. This could also be considered as the simplest form of a transkit.
Transkit - This is a more than a body shell, and generally involves a more complex modification. It also requires a plastic kit to finish, but usually will include far more than just a body. A new interior tub, seats and other parts are usually included. When you are done you will probably have a lot of the plastic parts left over (great way to start a parts box if you don't already have one).
Common transkits are changing from a 2 door body style to a 4 door, or station wagon, also a different year or make of vehicle (Chevrolet to Pontiac for example). As the plastic kit frequently is just used for the Chassis and running gear there will often be much more flexibility in the selection of a kit used to complete a transkit.
Full kit - This is a complete kit, it includes everything you need to build it, just like a plastic kit (although decals may still be needed). Full kits may not technically be complete, as some resin casters will sell wheels or other parts seperately allowing the customer to do a little personalization of the kit without adding redundant parts.
OK, on to techniques for working with resin. I put together a little walk through of how I build a resin kit, there are many options, this is just how I do it. Plastic and resin share most techniques, but there are a few differences.
#1 is glue, you will need to use a CA glue (super glue) or an epoxy. Regular plastic model glue will not have any effect on resin and can not be used to attach resin parts, luckily CA glue and most epoxies do work on plastic.
#2 is paint, resin often has an oily mold release left over from the casting process. Even if the resin caster does not use a mold release, unprepared resin will frequently repel paint, so resin needs some additional preparation be fore it is ready for paint. On the plus side "hot" automotive paints that can damage plastic will not usually hurt resin.
#3 resin is much more brittle than plastic. You can often trim plastic very closely with a sharp knife. When working with resin it is better to use a razor saw for removing large bits and a sanding stick for the final shaping. Cutting resin with a knife or sprue cutters may cause resin to shatter. When you are sanding a part check your progress frequenly, it is very easy to sand right into the part.
#4 resin dust is not toxic but it is an irritant, so it is best to do major sanding outside and a dust mask is recommended. If you can't sand outside, sanding over a box will at least make it easier to catch the dust for later disposal.
Other than these issues, there is not much difference between working with resin and plastic.
Recommended tools and materials
A plastic container large enough to hold your resin parts and enough liquid to submerge them.
Westley's Blech Wite, this is a tire cleaner you can find at most auto parts stores. This is my choice for prepping resin parts, but there are others.
TSP, and rubbing alchohol are other popular cleaning solutions.
Sanding sticks, sand paper, razor saw, epoxy and / or CA glue, model putty, paint.
I'll be going though step by step with a 1950 Jeep pickup from RMR.
Step 1
Seperate the parts, clean up flash. Thin flash may be trimmed away with a sharp knife, thicker flash should be sanded.
Step 2
Place parts into cleaning solution. Most of these solutions are very harsh on bare skin, so gloves are highly recommended. I prefer a container with a liquid proof lid to help avoid spills. Times very, I usually leave the parts overnight but if I am in a hurry a couple hours usually seems to be long enough.
Step 3
Rinse parts with warm water. I like to use a clean container filled with warm water to rinse the smaller parts as it makes losing parts down the drain less likely. A soft stiff brush like a toothbrush also helps clean the surface. I give the parts a final wash in warm soapy water, then rinse and let the parts dry. You can check the surface with masking tape, if tape sticks paint should as well, if the tape won't stick to an area you might want to go back and clean it some more.
Step 4
Hunt down and fill any bubbles or other imperfections. When I can I prefer to open bubbles from the inside and fill them with putty. This usually leaves the surface clean and unblemished which means less work for me.
Step 5
Do any additional sanding or filling. I find emery boards work well on resin.
Step 6
Based on your preferences, you may choose to do some assembly before painting. With this particular kit, I chose to prime before doing any assembly.
Prime your parts, any primer should work, but I personally have found Krylon and Plasticote seem to work better on resin than other brands I've tried. All resin is not the same though so a primer that works well with one brand may not work as well on another. I start with a light mist coat, then add another coat every 5 to 10 minutes until I have a solid coat of primer. Once the parts have been primed, there is little difference between working with plastic and resin except for the glue you are. Just like when working with plastic if you have painted the parts prior to assembly you should scrape the paint away from areas you will be gluing together.
From this point on there is little difference from building a plastic kit, so I don't have any more to say. Now go find an interesting piece of resin to work with and good luck.
Edited by Aaronw, 19 April 2010 - 10:39 AM.
