Develop - what's new from the Alpkit Design Team
By Pete Dollman
05, May, 2010
The single most important thing in a boulder mat is the foam. It is the foam that absorbs the impact of falls. So, what makes the perfect boulder mat foam?
We see foam as the most important part of your bouldering pad. Sure it may have a super funky design and all the features, but if the foam’s no good then you may as well not have it.
What is the best foam for bouldering pads?
In theory the ideal foam for bouldering pads is a thick, soft, high density natural PU foam (think gymnastic crash pads/mats at climbing walls) which will absorb energy slowly for a softer fall. Unfortunately this foam is incredibly heavy, so we have to make a compromise. It doesn’t matter how good your pad is if you break your ankle because you couldn’t be arsed carrying it to the problem!
How do we decide what foam to use?
You want your foam to cushion your fall and cover lots of your landing zone all the while being portable and durable. There are a few things we consider when looking for this balance.
We think of density as ‘hardness’, but a foam’s density actually tells us how durable and supportive a PU foam is. It measures mass per unit volume of foam.
Through flex fatigue testing, several studies have indicated that the higher the polymer density of the foam, the slower the rate of degradation and softening. A soft pad isn’t so supportive.
When to be wary
Very often, foam used for portable bouldering mats contains additives which artificially harden it for its density. The result is a lighter pad that still feels hard. Sounds ace, but this comes at a cost to durability because although the foam + additives is denser, the polymer density isn’t any higher and it’s the polymer density that counts.
This is also why the foam in your pads start to degrade and become soft after a couple of years of use, whereas the foam in your mattress (the same foam, fact fans) will last ten years or more.
So, should we look at density?
Good quality high density foam may be heavier and costlier, but it will last longer. Light hard foam is cheaper but will soften quickly!
So perhaps the weight of a mat is a better indication of its quality than its hardness?
Does surface hardness matter?
This is what you can feel when you stand on a pad or squeeze it in a shop and is a major contributor to the pad’s ‘softness’ sensation (which is how most of us gauge a pad’s quality).
In fact, it’s the deep-down support which carries much of the load and will do the business on bigger falls. This is not directly related to surface firmness: just because a mat feels soft, it’s not necessarily more likely to bottom out. It will, however, be much kinder to your body on smaller falls!
So where do we go from here?
We reckon the ideal foam should be soft on small falls, but very resistant to bottoming out when you hit it from height. To make this possible in a portable, durable crash pad, we make our pads from a layers of open cell and closed cell foam.
Open cell foam absorbs the impact of your falls. It’s a softer foam that makes up the core or bottom of your pad. It works because it’s made of irregularly shaped cells that are linked together and compress when you fall on them.
Closed cell foam distributes your weight across your landing surface so you don’t ‘bottom out’ (compress the foam so much that you hit the ground through your pad). It’s used for the top layer of your pad. It works because it’s made rigid, uniform cells that don’t compress much when you fall on them.
Two layers of foam is pretty standard these days, with a top layer of closed cell foam and a base of open cell. For pads designed for higher impact falls, manufacturers use 3 layers of foam (closed, open, closed) to give a second layer of protection when the risk of bottoming out is even higher.
Hati's beta on buying a bouldering pad.
Hebe, our UK-made designer, talks you through how we put together our range of bouldering pads
We have over 10 years of experience making pads, find out more about our design criteria.
A pad does not give you carte blanche to climb without due care and attention. If you're new to climbing outdoors, read these tips on climbing and falling.
Got specific needs? We make our pads in the UK so get in touch and we will do our best to help.
Looking after your bouldering pad, how to replace foam, repair your shell, clean and store it.
More pads are better than one pad! Using multiple pads brings its own challenges, Ashleigh explains what to look out for.
Mujo12 cm thick bouldering pad for up to high level falls, an ideal main pad for frequent boulderers with a hinge fold and an adaptable, versatile backpack carry system£174.99
Project15 cm thick uber-sized bouldering pad with a thermoformed back system for comfortable weight bearing; perfect for big boulders, big projects and big dreams; made in our UK factory£229.99
Origin11 cm thick taco bouldering pad for up to high level falls, an ideal main pad for frequent boulderers with an adjustable, adaptable rucksack carry system£159.99
Phud8 cm thick light and portable taco-style bouldering pad, ideal for whipping round your local circuit (or in Font if you’re lucky) or as a second pad; made in our UK factory£99.99