Prepping A Resin - Illustrated

Before any model can be painted, first it must be prepped.

Models in various stages of prepping.

Prepping is the fine art of readying a resin or plastic model horse for painting.  Seems simple, but a poorly prepped horse could have a bad seam line, distracting from an otherwise good paint job.  Or even worse, a badly prepped model may have issues with paint not sticking to the horse itself!

Because of these possible issues, and the time involved in prepping a horse correctly, many painters now ask for models to be prepped for them.  This has resulted in a nice side gig for "preppers" who work exclusively on readying models for custom painting.  The fee for prep of a model horse is usually very reasonable, considering the work involved.  Often, preppers only charge $30-$40 to prep a model.  However, the postage and insurance cost added in, going both ways, can make the total bill daunting, before an artist adds a drop of paint.  And then of course there is always the question "Is it good enough?"  Every prepper is human, and is sure to miss a spot here or there.  How do you know their standards are as high as your own?

There is a solution to this dilemma.  Learn the art of prepping.

Not only will you save money, you will know that the model has been prepped to YOUR satisfaction, because you will have seen exactly what it looks like before paint has been added.  If you have a closet full of unpainted resins, the amount of money saved can really add up.  Furthermore, once you learn how to prep, you can offer the service to other model horse fans.  Some painters will even swap prep work by others, for a paint job in exchange! 

Hobby preppers are always in strong demand, and prepping can be a great way to support your hobby.  After you have prepped your own models, ask for feedback from the painting artists and other collectors.  If they say the model was truly ready for paint, you're on the right track!  Then, I'd suggest starting by taking prep orders from locals first.  That way, if you miss a spot while you are learning, it's easy for them to pass the model back and forth for corrections.  Once you have prepped several models without complaint, from local customers, then you know that you're ready to take on outside orders. 

There is a very good guide on the Rio Rondo web site.  EVERYTHING HERE is from that guide!!!  

riorondo.com

Go to the bottom of the Home page where it says "General Info" and click.  Then, look on the left, for "How To Brochures".  Click there.  Scroll to the bottom where it says:

• Preparing Resin Cast Models for Painting--BR8

  Step-by-step guide to preparing a resin model for painting, including information on tools and supplies required.
  Resin Prep PDF approx 200k 

This is what you need to print out.  The only suggestion I have to change it, is personally, I do not recommend an X-acto knife for prep work, just too dangerous.  Please use Carbide Scrapers instead. 

All I am showing you here is the info on this sheet, but with some photos of the process.  This is how I prep models, but others may have different (better) techniques so keep an open mind.  Ask around to see what others do.

To start, I wash all models in hot, soapy water.  Make it as hot as you can.  TOO hot to comfortably soak your hands in is good.  Mold release is sometimes used in resin casting.  It is hard to get off a casting, and if left on, it will cause paint to lift and chip off unless it is totally removed!  So, soak them in HOT soapy water to get started.

Next, I pull out a model and make a paste of Ajax or Comet and water.  Douse an old toothbrush with this paste.  The idea is to rough up the surface of the model, on a microscopic level, to give it added "tooth" and to help remove the mold release.  I can't stress how important this first step is.

When you pick up the model out of the water, make sure you feel all areas.  Are there spots where it feels especially "slimy"?  This could be mold release.  You want the model to feel "grippy" when you finally rinse it off.  

Scrub a Traditional model with the Ajax or Comet abrasive paste for 5-10 minutes.  Seriously, THAT LONG.  And make sure you scrub in all the odd places, especially in the mane, the tail, and in the grooves of the face. Don't forget the legs!  Then dip it back in the hot, soapy water.  Feel like doing it twice?  Go for it! 

Next, rinse the model really well in clean running water and let it air dry completely.  Now, get used to this "clean and air dry" step, because you are going to do this a LOT.  I have tried using paper towels and regular towels, but nothing gives a lint-free finish like air drying.  However, if you do not let the model dry completely, what will happen is you'll get drops of water in the nostrils, inside the ears, and in the hair.

If you don't wait for the model to be REALLY DRY the primer will lift and it will be a horrible mess like this:

Water caught in the crevices caused primer to lift.  Be Patient!  Let it dry.

Primer can't stick to water.  If you don't wait for the horse to get totally dry, you will get hidden spots where the primer will just flake right off the horse.  That's because it was never actually touching the horse, it was sitting on top of a hidden bit of water.  Usually, this happens in "pocket" areas like inside the nostrils, inside the ears, between the hind legs, or in grooves of the mane and tail.  Do not get impatient!  You absolutely MUST wait this out.

For best results, do a little on each horse, every day, and rinse the models off and let them dry overnight.  This is why often prep will take me about a week, and why I work in large "batches" of models.  For best results, it is good to do a few hours of prep work each day, leaving plenty of air-dry time and making sure you look at the model with "fresh eyes" each session to catch all the stray seam lines.

After the initial cleaning, it is time to start removing seam lines.  Carbide scrapers are best, if you can't afford the entire set, three main ones will come in most handy.  Rounded like the end of a Popsicle stick, (CSO4 is my favorite but CSO1 also works) this levels seams like super-effective sandpaper.  A pointy ended tip, (CSO2) works great for tight areas.  Last one looks like a pencil lead worn out on the side, see pics above. (CSO3b)  

There are more designs available, but I generally use these three most often for prep work.  Price will run $35-$55 for scrapers, depending on if you get a few or the entire set.  Now it's time to use them!

Use your larger carbide scrapers to glide across larger seams.  For the inside of mane hairs, use the tip that looks like a pencil lead that is worn out on one side.  (CSO3b) This tip is great for cleaning out seam lines that run through manes and tails.  Also use little bits of fine sandpaper folded in half to help get in mane grooves.  Don't over-sand at this point.  Be thorough, but remember this is just stage one.  Getting too aggressive now will result in more work later.  

Don't forget to use a really BRIGHT lamp when working, otherwise you will miss a lot of seams!  A cheap clip on lamp from a hardware store and a bright bulb is fine.  When you are all done with the seams (or you think you are) wash again in hot soapy water, and let air-dry overnight.

The next day, it's time to add a layer of primer.  Use gray so you can see the seams better.  Prepare to be shocked!  Flaws are really hard to spot in white resin, but when you add gray primer, suddenly all the problems pop out at you.  Go as light as you can with the primer while still covering well enough to see the seams.

At this point you will probably be wondering what to do with all the uneven or recessed seams.  This is where, if you were to just sand them even, you might risk ruining the detail.  What you need is Spot Putty.  It is reddish in color, a paste in a tube, and sold in the auto body section of stores.  For larger areas, I will smear it on a large seam and smooth with a piece of paper towel.  For small areas, I use a little sculpting tool to smear it on small seams.  Do not get it on your hands, it's not good for you and it's also hard to wash off. 

When the paste is dry, sand smooth.  Now your seams should actually be fixed.  However, some models may have "pin holes" which are the most annoying of all prep issues.  Pin holes are too small to let primer cover them.  What you need to do is dab Gesso on a fine paint brush, dot it on top of the pin hole, then smear it into the pin hole with your finger.  (Gesso is non-toxic so feel free to use your hands if you need to.)

For larger areas, you can even brush on a layer of Gesso, making sure you dab the Gesso and really scrub it into the pin holes.  Often, pin holes can not be simply painted over, you need to really smear the paint into the holes.  (This step may take two or three tries to fill all of them in.)

Above:  What "pin holes" look like.

Below:  How to fix them with Gesso.

When you are done, mist very lightly with gray primer.  At this stage, the model is now prepped, but I generally find I missed a few small spots.  Fix these while you can.  Wash in hot soapy water (yet again) and let air dry.  After the model is totally dry, I do a final light coat of white primer, so the paint will cover more easily.

There, you've prepped a model!  It's a bit dusty, and kind of boring work but you'll make painters happy everywhere you go now, and if you want to get really good, you can even help out other collectors, and maybe, even make a few dollars prepping models on the side.