Evaporative Cooler Pads - Aspen versus Blue Foam

I was in line this morning at the local Hom-Mart with a huge roll of aspen cooler pads under my arm. I had left a trail of small white noodles all the way from the cooler aisle, and the guy in front of me turns around and says, "I use the blue foam ones, they don't make all that mess"

I wanted to tell him what I do for a living, and how I know about clogged cooler pumps, baskets and distributor tubes. I wanted to tell him about those speedometer cables to clean out the water lines.  The blue foam does not have the same surface area, so they don't cool as well. I use the blue foam on our commercial rentals at work only because we don't have the manpower to keep up on the maintenance.  I want Aspen on my garage because they work better.  I'll clean it out once a month.

I smiled and said, "I love the way the Aspen smells".  He paid for his stuff & left.

Flash back 2 days. My dog Max has been pretty aggressive trying to get in the garage door the past few days.  It has been around 100 outside, but I have a swamp cooler on the wall in the garage also.  It should be cool out there, what is his deal?

I could feel a wall of heat when I went through the garage door. No wonder Max wants inside.

I took out my trusty laser thermometer & shot at the throat of the cooler.
The photo sucks because of the flash, but the display says 89F.

That's NOT good. It's only 96 Outside. Only 7 degrees drop?

I checked the supply temp on my main house cooler:

That number looks right.  It's about 96F outside, and humidity is in the 20's. I'm getting a 30 degree drop on the main cooler, so what is going on with the garage?

Must be a pump problem, right?

I pulled a pad frame on the garage cooler. The pump was running full blast, but the outer surface of the pads was dry. Only a small ribbon of moisture went down from each drip hole in the top of the frame. Everything else was bone dry.
No water, no evaporation, no cooling.

My main cooler has aspen pads, so that's why I was at Hom-Mart earlier.  I knew that Aspen cooled better, but I had never measured it in a controlled test.

I dumped the blue foam, installed the 3 Aspen pads & wet them a bit with the garden hose before I put them back in.

The ambient temp went down a little while I went to the store:

This is the garage cooler about 5 minutes after I put it back together. The pads were not fully soaked yet.

This is final temp check, about 15 minutes run time. Pads were fully wet & the float had stopped hissing. Getting 22 degrees drop. I'm pretty satisfied.

You may ask, why is the main house cooler so much cooler? That photo showed 30 degrees temp drop from ambient.
The reason is the main unit is a 5000CFM down draft.  There are 4 pads, so the airflow is slower over more surface area of padding. Longer contact time allows more temp exchange. The garage cooler is a wall mount 4000CFM. There's only 3 pads, and the air is moving faster.  Less contact time. That's it.

So the next time you're at Hom-Mart in the cooler aisle, you can answer with confidence.  Aspen pads cool better. You read it on the Internet, so it's true right?