The inside of the pad (or the backing) can have a leakproof liner that works like a disposable pad does – in helping prevent the blood from soaking through the layers of the pad and onto your underpants. Some people do not need this, and some do. It depends on how heavily you bleed and how your flow is naturally distributed over the surface of the pad. If you tend to bleed in one small area, or “gush” then you may find that you soak through a pad too quickly if it’s not waterproofed. A Water/leak “resistant” fabric isn’t completely waterproof, but will form a layer that is more resistant to leaking than the other fabrics in the pad.
Some people are concerned about the “breathability” issue of waterproofing. Comparing a waterproofed cloth pad to a disposable isn’t the same. A waterproofed cloth pad isn’t going to be as sweaty as a disposable. The issue of letting the skin breathe is a debated one. Does skin really need to “breathe” as such? does putting on a cotton topped pad that has a PUL layer in it, stop the skin “breathing”?. If you suffer from thrush or excessive sweating then you might want to avoid synthetic waterproofing, and opt for something more “breathable”…. but even with “PUL” its not like having a plastic underpants on.
When they talk of “Breathability” in plastics such as PUL, they don’t mean that you can breathe through it. It means that the waterproof membrane lets no water through, but will allow a little air through (on a microscopic level). This “airflow” is just enough to lessen the sweatiness compared to a PVC or other non-breathable fabric (like what is used in disposables). It was designed for uses such as raincoats, where the fabric is designed to prevent the wearer getting too sweaty inside the coat. If you look at a statement like the one Goretex makes, it explains this: “The GORE-TEX® membrane is the heart of all GORE-TEX® products. It contains over 9 billion microscopic pores square inch. These pores are 20,000 times smaller than a water droplet, but 700 times larger than a water vapour molecule, which makes the GORE-TEX® membrane completely waterproof from the outside, while allowing perspiration to escape from the inside“.
The other natural fibre layers in the pad will allow for some airflow through the pad. In a “turned and topstitched” pad, the waterproofing only comes partly up the side giving plenty of surface for airflow, and an overlocked/serged type pad has the sides (cross section) open too. Airflow doesn’t have to be just from between the legs up. Some people feel a difference in a waterproofed pad over a completely natural one – others don’t. Some can feel hotter and sweater with a PUL pad on, and some can feel that fleece backed pads feel hotter (as they are fluffier and can trap more heat). The more open weave a fabric is, the more “breathable” it will be… but that also means less waterproof. So it is a trade off between airflow/natural fibres and leak protection. As with everything, it is personal preference.
As for the argument over PUL not being good for the environment, it’s worth noting that polyester fleeces (Windpro, Blizzard, “Antipill” etc.) are also synthetic. So are no different in that respect. In fact, the highly effective DWR Windpro is also coated in a water-proofing chemical in addition to the synthetic fibres of the fabric. There are studies which show that fabric such as synthetic fleeces are shedding microfibres into the waterways and causing significant problems. (Link, Link, Link) So out of the 2, PUL is likely to be less damaging to the environment.
Some points to consider with waterproofing or not.
- Thickness – do you want the pad to be as thin as possible, or are you happy to have it a bit thicker.
- Waterproof or water resistant – if you have a lighter flow you may like to use something water resistant, if you have a heavier flow and.or really don’t want to risk leaks, you may prefer something waterproof.
- “Breathability” and heat – do you have problems with thrush or want a lot of airflow. Do you want a pad to be as cool as possible or is that not an issue.
- Natural Vs synthetic – for Environmental or personal reasons, do you want to avoid synthetics completely, or as much as possible. Or are you fine with synthetics
- Comfort/Lifestyle – Do you want to stress about leaking through a pad. Do you need to wear a pad for a long period of time and not be able to check regularly.