Saturday, January 7, 2017

Prepping 101

If February is National Model Painting Month (NaMoPaiMo), then it's reasonable to assume that January is National Model Prepping Month. I asked artists to share their best prepping tips on the NaMoPaiMo Facebook page, and Anne Field responded by sending me this wonderful article. Thanks so much, Anne!

How to Prep Like a Pro

by Anne Field

Prepping is a very important step in creating a beautiful finished custom model. But what is prepping? The easy answer is that it is preparing your “canvas” to receive paint. However, it is more involved than slapping on a coat of primer. Prepping includes washing the model, sanding seems, filling pinholes and occasionally a bit of re-sculpting. The last step is a coat of primer and then it’s off to the painter. The desired end result should be a nearly perfect equine sculpture without any weird lumps, bumps or divots that you wouldn’t find on a real horse. While nothing in life (or art) is ever perfect, a sub-par prep job really takes away from the beauty of a finished piece.

First let’s take a second to talk about tools and supplies. The things that I find indispensable for prepping are: Comet, Plasti-kote (now Valspar) sandable primer (though most any sandable primer will do), a carbide scraper from Rio Rondo with the butter knife shaped tip, 320 grit sandpaper, 600 grit sandpaper, Liquitex modeling paste and some water. If I need to do any sculpting I use Magic Sculpt. Most two-part epoxies are good, I just find Magic Sculpt easier to work with.
After choosing a model to prep, the first step is to give it a bath. I always use Comet (although any scrub with bleach is fine) because it will remove leftover mold release from the surface of an artist resin. I sometimes wash OF models before I prep them because you don’t know what might be on them from the factory, and some of the things they “pick up” in shipping and storage will do weird things to your primer. 
After the bath and a thorough drying, I spray on a light coat of gray primer. Sometimes I'll scrape the seems first, but a coat of gray primer helps make the imperfections jump out at you.

During the photo sessions for this article, I was working on an OF resin. I didn’t give it a bath and the primer “fish-eyed” pretty badly. If that happens to your model or you get drips from too-thick primer, don’t touch it! Let it dry completely and then sand it smooth. That is an easy fix. If you try to smooth it while it’s wet it will become a gummy mess and will take a very long time to smooth out. Or you might make such a mess that the horse will need to be stripped. When primer mistakes happen, waiting can be very hard but the alternative is so much harder.
The  light coat of primer allows you to see seems and little lumps. Take your carbide scraper and gently scrape them off. I always start with a very light touch because it’s always possible to take off more but if you gouge a hole in the model you will have to fix it. Be very careful when scraping resins. The scraper will work on them as if it was butter. It really is very easy. Plastics need a bit of a firmer touch but if you press too hard you will get a very ugly result (that looks sort of like a ladder) and not a smooth spot like you are trying to get. So start out gently and see what works best.

After all the seams are scraped down take the 320 grit sandpaper. I rip it into small squares, maybe one and a half inch by one and a half inch. You want it to be small enough to get into small spaces but big enough to hold. Take a small piece and start sanding anything that isn’t smooth: the seems you have scraped, scratch marks, and anything else that looks less than perfect. It’s always recommended to wear a respirator or mask while prepping because the dust isn’t good for you. If you do this you will need to keep a large, soft paint brush handy so you can sweep the dust off the horse and check your progress. I have found that the easiest way to sand the horse without causing more damage (and more work for you) is to sand in small circles. There are some areas on the horse where this just won’t work but usually the tight areas don’t matter quite as much because any tiny imperfections won’t really be visible. You don’t want to scrape lines into the horses back though! After I sand thoroughly with the 320 grit paper I will go over everything with the 600 grit to make it nice and smooth. 
Let me take a minute to talk about sandpaper and sanding. 320 and 600 are not the only grits that work well for prepping horses. They are just the types that I have found that work best for me. I have used 220 and up through 2000. But the ones that do the most for me are 320 and 600. I have even done all of the sanding with just 320 grit. Once it gets soft from use and a bit caked up with resin dust it won’t make as many scratched on the horse. A light tough with “used” 320 grit can be the same as sanding with 600 grit. Part of learning to prep is practice. Experiment with different sandpapers and find what works the best for you. You also want to try a lighter and firmer touch with each kind until you find the way to prep in the most efficient way. Everything gets easier with practice.

Now it’s time to discuss pinholes. Those are tiny holes in the surface of artist resins caused by air bubbles that were present during casting. They are not hard to get rid of but they can really ruin the look of your finished piece if you leave them. As with other aspects of prepping, some horses have little to no pinholes, while others seem to be almost all pinholes. 
If you see any pinholes, grab your Liquitex modeling paste. It is just marble dust in a polymer base so isn’t toxic like Bondo or other fillers. The plus side of this is you can touch it with bare hands. I have always had trouble smoothing body filler while wearing gloves. Anyway, the paste dries very quickly so never work from the open jar or you will ruin the entire container. Just take a dab out and put it on your workspace (I use a small piece of tinfoil). Then you can either smooth it onto the holes with a paintbrush or your finger. Once it’s on dip your finger into the water and smooth out the paste. You don’t want to push too hard or use a lot of water because you can pull the paste right out of the holes. You do want to try to get it as smooth as possible because you will have to sand it smooth after it dries.
Once you've scraped all the seems, filled the pinholes and sanded everything as smooth as you can make it, spray on another coat of primer. Repeat the steps as many times as needed to get a smooth finish. Then when you think it’s done put it down for a day or two.

Why do you need to put it down and leave it for a few days? Prepping can be a very tedious job, especially if the horse you are working in starts out very rough and needs a lot of work. After awhile you will get to a point where you really want it to be done, and your eyes may not see the flaws anymore. If you put it down for a bit, and then go back and look at it with “fresh” eyes, sometimes you will see flaws you didn’t notice before. And sometimes you will get lucky and find that you actually are done. 

If you do find more things that need fixing, smooth, fill and sand until they are better. Then more sanding and repeat as needed.


  1. This is amazing!!! Thanks so much for putting this on!! Thanks to you too Anne!!

  2. Thanks for the excellent, well written article Anne! Your concise and insightful writing makes me want to dive back into some much-needed prepping!

  3. Great article, I find it very helpful. Tkanks tons!

  4. Very helpful article - thank you Anne and Jennifer!

  5. Wow, this is a wonderfully written article! Thank you, Anne and Jennifer!

  6. Thank you...I always put on the primer just before I think I'm ready to paint and then sure enough, there are all the flaws. I am also guilty of picking up a body and just noodling around with pastel or paint and the next thing you know I have a horse I like that I never what...