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When sunscreens were first introduced in the 1970's, the "Sun Protection Factor" (SPF) was a great step forward in helping people understand how to get better protection. Since then, the industry has made great improvements both in the chemical formulations and in understanding how the skin protects itself.

Research done by Sawyer's technical partner CCI Inc. has resulted in additional logic and technology which focuses on matching the formulas to the condition of the skin at the time of application. Quite simply, we have learned that if the skin is already wet or has begun to elevate in temperature, it may not accept traditional sunscreen formulas. CCI was able to divide this advanced understanding of sunscreen technology into two distinct formulations.

The Stay-Put SPF 30, offered exclusively through Sawyer, bonds excellently to skin which is cool and dry. You will find no better sunscreen on the market in terms of comfort in wearing and ability to hold in extreme conditions, such as swimming, sweating, or abrasion.

What has been discovered in recent testing is that no formula, not even the Stay-Put SPF 30, could hold up to the challenges of an active person whose skin is already wet or heated. The conditions we tested are well beyond those required to achieve an FDA rating for sunscreens. As a result of this study, CCI developed for Sawyer the Stay-Put SPF 50 formulation.

The likelihood of a serious reaction is significantly higher when applying sunscreen to hot skin.  Sunscreens applied to extremely wet skin generally work poorly as the skin never really accepts them.  However the Stay-Put SPF 50 formula has the added protection of Titanium Dioxide and is designed to hold in extreme conditions, even when applied to moist or heated skin. Of course it is preferable to bring skin to a cool and dry condition before applying a sunscreen, but when that is not possible, we recommend the Stay-Put SPF 50 formula.

It is worth noting that the Stay-Put SPF 50 is a little thicker than the SPF 30 formula. While the SPF 30 disappears into the skin, the SPF 50 clings harder to the upper layer of skin. This is necessary because the areas of thinner skin do not have the deep layers in which to hide the sunscreen. Since the SPF 50 formula is thicker and does not penetrate as deep as the SPF 30 formula, it is much more likely to hold your sweat making it feel greasier, but still release the sweat as you cool down. This is why we generally recommend the SPF 30 formula for most applications and reserve the SPF 50 formula for extreme conditions and in cooler ambient temperatures.

As we continue to learn more about the skin, and as we continue to develop new chemicals to improve your sun protection, you can count on CCI and Sawyer to keep you at the forefront of advanced protection.


May 9, 2022

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My only complaint is that eventually, backflushing won’t be enough. These can clog up after some time and no amount of back flushing will fix its low flow. I went through 2 on the AT. However, it will attach to Smart Water Bottles and most bladders!

Anna Hamrick


Built for backcountry reliability and portability, the Sawyer Squeeze filter is our pick for the best portable water purifier.

Pete Ortiz


The Sawyer Squeeze was (by far) the most common Pacific Crest Trail water filter this year – for the fifth year in a row. It’s a $39, 3 oz / 85 g hollow fiber filter that rids your drinking water of protozoa and bacteria (and floaties). It can be used with Sawyer bags (included with the filter) or with compatible water bottles (Smartwater is the bottle of choice for many hikers).

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