I am building an Ultra Forge Dragon for a December Client. I figured I'd create a WIP for it, as it is an awesome sculpt and looks to be a fun resin project. Prepping resin is a bit different than prepping plastic, but once you get the hang of it you can build gorgeous models.
This is the actual resin kit that I will be working with. It has 15 pieces and is suppose to come with magnets for the wings but my kit was missing them. This was not too big of a deal, as I have dozens of neodymium magnets in several sizes but it was advertised as part of the kit and this one was missing them.
Excluding missing parts or major flaws, you should expect your resin kit to arrive with minor flaws and flashing. Resin replicates intricate details from a master model, but it will also carry over even the slightest casting deviation into the final product. Air bubbles tend to be the primary issue confronted when casting in resin. Most professionals attempt to avoid air bubbles by degassing their resin to 29 in HG (inches Mercury) after mixing it, then cure their resin at 60psi or greater. Yet try as one might those evil little bubbles almost always seem to find their way into the production model.
This picture illustrates three of the most common issues encountered when working with resin casts.
The air bubble is located under the neck where the body joins to the head. It is a simple fix with Greenstuff, a two part epoxy that once shaped, cured, and painted is difficult to detect. It should be noted this is the only 'major' flaw I found on this model. A testament to the craftsmanship that went into designing, sculpting and casting this model. I often feel like its the 'resin lottery' when I inspect a new model. It can be a real PIA when there is a serious flaw in the model. One in which the whole build can be delayed by weeks while you send and receive corrected parts from the manufacture (it particularly sucks if this company is in Nottingham, England).
The second issue often present in resin models is joint cavities filled with resin. This joint connects an arm to the main body. This model is so large I actually took my power drill and a 3/16 bit to drill it out. Normally you would use a pin vice and at best a 1/16 bit, but this is a Dragon and it needs a monster bit (well monster for model building).
Flashing is the third issue normally encountered in resin modeling. Flash is not unique to resin and every model builder knows to clean up mold lines prior to assembling a model. This excess resin or mold lines on a model result from the casting process. I scrape and sand the model until I am aesthetically satisfied by the look of the model parts. The one important aspect of removing resin flash is remembering its toxicity.
Resin is dangerous if inhaled!
Wear a dust mask and if at all possible sand and scrape your model outdoors. If you clean it indoors the dust will settle on surfaces, and return to the air every time you disturb the surface. It is not that big of deal so don't get paranoid but you normally only get one pair of lungs, so you may want to keep them as healthy as you can.
The last prep issue normally encountered with resin modeling is warping. Resin is heat sensitive and if the temp is high enough it will bend and warp out of shape. This UltraForge Dragon shows no sign of warping. If it did or I wanted to mod part of it, I would soak it in hot water (150F/65C), remove it (with gloves on my hands), bend it into place, and then submerge it in cold water. The resin will now hold the new shape.
Once the flash is removed and all minor flaws have been corrected it is time to remove the 'mold release' from the model. A release chemical is applied to the mold so that the cured model 'releases' simply from it. As the resin cures in the mold the 'mold release' is also passed onto the surface of the model. This needs to be removed before gluing or painting the model.
MOLD RELEASE MUST BE REMOVED FROM THE MODEL!
You can skip everything else in the model prep, but you must remove the 'mold release'. If it is left on the model, the paint eventually will chip off the model or the glue may fail over time. I find undiluted Simple Green and an old tooth brush is the best technique to remove the 'mold release'. I normally soak the model parts (fully submerged in the undiluted Simple Green)for four hours. Then I scrub the model, taking care to avoid using the brush on delicate parts of the model. Finally I rinse it under warm water, remember if the rinse water is too hot you could warp the model. Once it is free of mold release I let it air dry fully before I assemble or prime it.
Notice the above picture of the Dragon head. If I ran my brush along those delicate teeth (well delicate in this world, fearsome in the game world), I would probably damage them. Soaking the head for 4 hours in undiluted Simple Green with a five minute warm water rinse, will suffice for delicate aspects, such as the teeth, on this model .
Once the model is dry test to confirm the 'mold release' is gone by rubbing a CLEAN finger on the model. Mold release will feel slick, a properly prepped resin model will no longer feel slick but slightly tacky to the touch.
That's it, that's my process for prepping the model for assembly and priming. Next time I will cover assembly of the dragon: pinning, gluing, and priming.