As a general rule, bloating is something you want to avoid.  Whether it's in your Breyer models, or elsewhere!  But in summertime, if you have a scrap model that's not good for anything else, some hobbyists like to purposefully bloat their Breyers just for laughs.

Bloating in Breyer models is a permanent condition.  It happens because the models are hollow.  If they are subjected to heat, with no way for the heated air to escape, the plastic (softened b y the heat) will begin to bulge and deform in unpredictable ways.

Newer models have an air hole hidden somewhere (often in the nostril, as is the case with my Sham pictured above) to prevent this from happening.  Older models do not have an air hole, which caused many cases of bloating in the past.

Bloating has led to the destruction of many otherwise wonderful models, either through thoughtlessness or through a disaster.  I have heard many sad stories of entire Breyer collections wiped out in a house fire - not because they were burned, but because the extreme heat caused the models to bloat.  Models accidentally left out on the driveway or in the rear window of a car can likewise be accidentally bloated.

In fact, these accidental bloating cases are the source of most bloat-damaged models which you can find for sale on eBay.  They usually go for a song, since not even the remodelers can find a use for a bloated body.  

If you have a scuffed, damaged, or otherwise unloved (and ideally unlovable) Breyer, and you're feeling a little bit demented, why not try bloating it?  With heat waves striking all across the country, this is a great way to take advantage of the extreme temperatures!

The first thing you need to do is locate the air hole - if your model has one - and plug it.  Any type of clay will do for a plug.  The air hole is often in the nostril, but it may also be under the tail (how graphic!).

Now, put it somewhere hot.  As hot as possible!  Standing it on the blacktop in direct sunlight may work in places like Arizona.  Other hobbyists have reported good results from leaving it in the back window of the car for several days.  One nasty case of bloat was encouraged along by putting the horse inside a cooler, inside the car for several days.  (The idea behind putting it in a cooler is to help keep the model hot overnight, when it would otherwise cool off and stop bloating.)

If you don't live somewhere hot, you can also try gently heating your Breyer at home.  I SAID GENTLY.  I have heard horror stories from collectors who tried bloating their models in the oven or the microwave.  The best case of manually-inflicted bloat reportedly came from someone who used a pot of boiling water and a pair of tongs.

Some great bloats I found on the BLAB forums:

The World Famous Bloaty!  Arguably the horse that started it all.

Fightin' Bloaty

Midnight Sun, now with stallion neck!

American Quarter Horse Stallion gets baked

And the cream of the crop, El Excedrin and Don Qu Bloatie!