Saturday, October 12, 2019

Back in the Saddle Again

 Ok, long time, no post, but I finally found some time, energy, and whatnot to not only work on some models but also create a blog post! Today, we're going to see one technique for lengthening the back on a hollow plastic model.

Likely one of the most common flaws seen in model horses is a back that is too short (or too long) Ideally, people want live horses to have nice, short, strong backs for athletic ability and overall health. As sculptors, we tend to want to emulate the ideal, so backs on most model horses are usually “perfect.” However, real horses are rarely ever perfect. And back length can vary depending on breed and gender (mares tend to have longer backs so they have room for growing babies).

In some cases, some breeds actually have longer backs as part of their breed standard. Some working draft breeds (Suffolk Punch, Breton, etc.), and riding horses (Akhal-Tekes, Criollos) want longer backs for specific reasons. Today’s example will focus on the Criollo and its current trend of having a nice, long back and short legs to help them get closer to the ground for agility purposes. 

I found most of my pictures of Criollos from the Cavalo Crioulo Facebook Page.

The model we’ll use today is an Alborozo, considered one of Breyer’s best molds, especially as an Andalusian. Some will like to paint him up in fun, wild colors and patterns and she him as a Criollo, however to be more accurate to a true Criollo, he needs some minor surgery. Andalusians and Lusitanos have much shorter backs and longer legs more in tune with a warmblood than the stock horse type that the Criollo is. Though they share a common ancestor, selective breeding and possibly some outcrossing has taken them down separate paths.


Seeing their differences lets us know what we need to change. Thankfully, Criollos have much the same head as Iberian horses, a very similar muscle type, and Alborozo has some nice, fairly short cannons that we can totally fudge an Alborozo to be a Criollo. But you’d be hard pressed to find a good working-type Criollo with a back so short. So… rev up your saw! We’re doing back surgery!

First, pencil in a guide line so you know where to cut. Selecting your spot to cut helps so you don’t accidentally cut into something you want to keep and gives you a better visual about how you’re separating the back. You can use a hand saw (hack saw) or use a cutting wheel on your Dremel or preferred power rotary tool. Be very careful and remember to use eye protection and face mask to prevent plastic shards from flying in your face and from breathing in the fumes caused by the friction on the plastic. Some of these plastic bits will literally melt and be quite dangerous!

If at this point you were wanting to *shorten* the back instead of lengthening it, you would just cut down the barrel again however much you were wanting to shorten it. Once you’ve fully separated your model in half, tear up and remove any excess shards

Next, use a heat gun to heat up the edges of your cut to make them soft and pliable.

After the edges are heated up, use pliers to crimp the edges inward.

This is a very important step. In order for the epoxy to have the best chance of staying on, we need the edges both rough and inverted so there’s enough thickness of the epoxy to have the best grip. If you just join the two ends and try to lay some epoxy over the top, after sanding down the epoxy to smooth it out again, it’ll be so thin it’ll be weak and subject to cracking. Plastic is much more sensitive to heat and could and can shrink and swell. Not to mention the epoxy will have no grip and nothing actually holding the two sides together.

What happens if all you do is meet the plastic and not go over it. BIG crack!

Next, use a sanding drum to rough up the edges even more, both inside and out. This is again, very important to help the epoxy to adhere to the plastic. Make sure to remove any excess burrs and shards off. You can also use some rougher texture sandpaper (~100-200 grit) to help remove them while also keeping it rough. The rougher the better, all of this gives the epoxy an ability to anchor itself and embed itself into the plastic.

Now your model is ready to be joined again!

The back may indeed look shorter at this time, but that’s fine, we’re going to be determining how long or short we want out back by using a simple cardboard roll tube, like from paper towels, toilet paper, or in my case, a tulle spool.

Little long here, you can cut the tube down to the right length.

This will help keep the length exactly how we want it as we join the model back together by creating structure and also keep the model hollow, keeping it light but also allowing air flow to still go between the front and back halves of the horse so we prevent bloat. Bloating can happen when air trapped in a model cannot regulate temperature in relation to the outside. If the air inside is hotter or colder than the outside, the plastic can swell or shrink, causing the more stable epoxy to crack. This is why it’s important to have a small pinhole somewhere reaching the empty cavity inside so air can flow freely.

To help your tube stay in place and create some grip for the epoxy, cover it in a wrinkly layer or two of aluminum foil

You can then place the foil covered tube in the body and fit the two halves together. If you wanted to give the model a new tail, I would suggest rooting it first before joining the two halves together and it will make it much easier to do so while you have the model cut in half. You can read more about rooting tails in another blog post of mine (coming soon).

Once the foil tube is in there, stuff little snakes of epoxy between the foil and the inside wall of the model’s body. Try to fill it in as best you can and smoosh it in really good.

Next, layer more epoxy over the whole thing, try to fill in the gap as best you can but if you need to do another round of epoxy for a final surface smoothing, that’s just fine. By getting both under and over the plastic, we've effectively created a good, locked in grip to prevent cracking later on.

It doesn’t matter if it’s lumpy, you’ll need to sand down any hills and valleys later anyway. I suggest using a Dremel to do so, and to go ahead and keep it pretty rough so when you do add your final top layer of epoxy to smooth everything out, the 2nd epoxy layer has some good tooth to grab onto. So divots, gouges, scratches are fine.

Finally, you can add your final thin surface layer of epoxy to fill in any gaps, valleys, and scratches, smooth it out as best you can with rubbing alcohol, let it set, and sand smooth with a finer grade of sandpaper (about 320+) to blend it all back in with the original plastic. His back is done! 

It's a subtle lengthening, a Criollo's long appearance is more in their short, stout, strong legs, but it was definitely needed. Now just to fix up everything else (like his legs, neck, hair, etc.) before he's actually finished.

1 comment:

Heather M. said...

Great tutorial Ms Cindy! Totally fascinating- I've never CM'ed a horse in this way so I like this info :)