山と道

UL Rain Pants

81g

¥17,000 (PU Sosui) / ¥18,000 (PU Shinsui)

Introduction

World’s lightest three-layer rain pants

Our UL Rain Pants are perhaps the world’s lightest three-layer waterproof rain pants. Developed specifically for hiking and fast packing, they are as light as regular wind shell pants and easy to move around in.

We offer two different material choices: the ultralight, polyurethane-based, hydrophilic, and non-porous Pertex Shield (PU Shinsui), and the well-balanced polyurethane-based hydrophobic and microporous Pertex Shield Pro (PU Sosui).

– Perhaps the world’s lightest three-layer rain pants
– Two choices of materials with different features
– Hypersonic welding to minimize the sewing
– Slim look
– Doubles as windshell pants

PU Sosui - Red
PU Sosui - Deep Forest
PU Sosui - Blue
PU Sosui - Navy
PU Shinsui - Ebony
PU Shinsui - Nomad

SPECIFICATIONS

Made in Akita, Japan

Material:
Pertex Shield Pro (PU Sosui)
Pertex Shield (Pu Shinsui)
Weight (Size M):
99g (PU Sosui)/ 81g(PU Shinsui)
Size:
XS / S / M / L / XL

Product Story

Akira Natsume, Yamatomichi Founder

On cloudy and chilly mornings I used to wear windshell rather than rain pants because rain pants looked baggy and not very cool and were often inferior in terms of breathability. Rain pants were not something I wanted to use unless it was absolutely necessary.

But then we started testing this three-layer, ultrathin, waterproof, and breathable fabric and it really surprised us in a good way. We decided to make a pair of comfortable and lightweight rain pants that can be used not just when it’s raining, but also only chilly days when you need something to block the wind.

Our UL Rain Pants are not suitable for winter backcountry skiing or rock climbing as they are made of ultrathin materials, but I personally think that the most interesting products tend to be specialized in certain areas, which consequently means that they are not always flawless.

That said, the UL Rain Pants’ lightweight is a great advantage. It is one of the lightest pairs of three-layer waterproof rain pants that I know of. (Perhaps the lightest?) They are so light that you almost forget that you carry them in your backpack.

Among many waterproof and water permeable materials that were available for us, the polyurethane-based hydrophobic and microporous Pertex Shield Pro seemed to be the best in terms of superior breathability and waterproof performance compared with the regular normal Pertex Shield. The regular Pertex Shield is however significantly lighter than the “Pro” version.

Pertex Shield or Shield Pro? We couldn’t decide so we decided to make two versions. Both are three-layered, comfortable, lightweight, and surprisingly flexible. Personally, I would choose the regular Pertex Shield, as my focus is mainly on keeping my base weight low. But I usually recommend our customers to get the well-balanced, but slightly heavier, Pertex Shield Pro.

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Form and Function

Supersonic Welding

The seams of our rain pants have been welded together to minimize any rain seeping in through the seams. The ultrasonic-welded seams have been reinforced with seam tape for added strength.

Details

Material

Two Different Materials

Our UL Rain Pants are available in two different fabrics: Pertex Shield Pro (PU Sosui) and Pertex Shield (PU Shinsui). Both are three-layer, water-resistant, and breathable materials, but each has a different membrane structure, material characteristic, and moisture-permeable mechanism.

Pertex Shield Pro(PU Sosui)

Pertex Shield Pro is a polyurethane-based hydrophobic and microporous membrane. The “hydrophobic” material has high water repellency, and the “microporous” means that it has a number of very small holes (pores).

These pores are too small for liquid water (rain) to enter, but large enough for vapor (moisture from your body) to get out. Pertex Shield Pro effectively vents the moisture within the clothes from the pores, achieving superior breathability.

According to our test at our Yamatomichi Lab, Pertex Shield Pro prevents excessive temperature rise even during heavy exercise, while keeping a constant temperature when it rapidly gets cold. According to the information provided by the manufacturer, the Pro version is more durable than the regular Pertex Shield.

Pertex® Shield Pro (PU Sosui)

Material:
Pertex Shield Pro (100% NYLON)
Material:
Pertex Shield Pro (100% NYLON)
Weight: 58g/㎡
Surface: 10d/10f x 10d/10f+30d, ripstop
Linning: 7d tricot
Water-repellent finish by C6 DWR

Specs:
Tear strength measured by JIS L 1096 D (Pendulum method)
Vertical: 1.0kg, Horizontal: 0.8kg

Tensile strength measured by JIS L 1096 A (Strip method)
Vertical: 27kg, Horizontal: 19.8kg

Breathability measured by KES method
270 or more

Water-permeability tested by JIS L 1099 A-1
11280g/㎡/day (Our measured value)

Water-permeability tested by JIS L 1099 B-1
20000g/㎡/day (Catalog spec)

Water pressure resistance tested by JIS L 1092 B
20000mm (Catalog spec)
https://www.pertex.com/fabrics/shield-pro/

*The PU Sosui uses ultralight and thin microporous material, the Pertex Shield Pro. Vaseline, insect repellent, and ethanol-containing substances such as hair creams, cosmetics and sunscreens may stain the fabric. They may also hinder the water-permeability of the fabric. Visit here to remove the oil stains. 山と道JOURNALS『山と道修理部通信#2 レインウェアの油脂汚れをきれいにする』

Pertex Shield(PU Shinsui)

The Pertex Shield uses a polyurethane-based hydrophilic and non-porous membrane. Though the membrane has no holes or pores, it has a strong affinity to water, allowing the water to sink into the membrane easily.

In other words, the membrane absorbs the moisture within the jacket and then allows it to evaporate. It works like a towel that absorbs water, and then dries by itself.

The greatest advantage of Pertex Shield is its lightweight: The membrane is non-porous, so the fabric can be extremely thin and light. Our experiment has shown that it quickly lowers the humidity within the clothes immediately after being worn, but the humidity will gradually increase after a while. For this reason, you may feel more humid compared with the Pertex Shield Pro material.

Pertex® Shield (PU Shinsui)

Material:
Pertex Shield (100% NYLON)
Weight: 47g/㎡
Surface: 7d/5f x 7d/5f, ripstop
Linning: 7d tricot
Water repellent finish: C6 DWR

Specs:
Tear strength measured by JIS L 1096 D (Pendulum method)
Vertical: 0.8kg, Horizontal: 0.7kg

Tensile strength measured by JIS L 1096 A (Strip method)
Vertical: 22.8kg, Horizontal: 21.2kg

Breathability measured by KES method
270 or more

Water-permeability tested by JIS L 1099 A-1
5568g/㎡/day (Our measured value)

Water-permeability tested by JIS L 1099 B-1
20000g/㎡/day (Catalog spec)

Water pressure resistance tested by JIS L 1092 B
20000mm (Catalog spec)
https://www.pertex.com/fabrics/shield/

Categorization and Characteristics of Waterproof and Moisture Permeable Material

The materials of waterproof jackets are generally made of multiple layers of fabric, that is, a waterproof and moisture permeable membrane is sandwiched between a water repellent, durable surface layer and an absorbent lining next to the skin. The membranes are roughly categorized into two groups according to the waterproof and moisture permeability mechanism: The hydrophobic, microporous membranes, and hydrophilic, non-porous membranes.

The hydrophobic, microporous membranes have a number of very small holes (pores) that are too tiny for the liquid water (rain) to come through, while allowing the vapor (moisture from your body) to vent. They are made of water-repelling ePTFE (expanded polytetrafluoroethylene, AKA, Teflon) or hydrophobic polyurethane (PU).

The most common ePTFE material is the eVent, and Pertex Shield Pro that we adopted. Polartec NeoShell is also a good example of a hydrophobic PU membrane.

On the other hand, hydrophilic non-porous membranes have no pores, so they permeate the moisture by absorbing the vapor within the clothes and evaporating it outside. Pertex Shield that we use, HyVent Flyweight by The North Face, and dri1 by Norrona are all non-porous membranes.

Gore-Tex, the most famous waterproof and breathable material, has a hydrophobic and microporous membrane with a hydrophilic coating. The purpose of the coating is presumably to prevent the contamination that can hinder the membrane’s performance, but due to the coating, it is inferior to non-coated hydrophobic, microporous membranes in moisture permeability. That said, Gore-Tex has many variations and it is probable that each product has a different level of coating depending on the exact specifics of the material.

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Test at the Yamatomichi Lab

We have conducted thorough research on rainwear over a year at our Yamatomichi Lab. The result is available online at the Yamatomichi Journal (Japanese only), full of independent research, experiments and new findings.

#1 土屋智哉(ハイカーズデポ)x 夏目彰(山と道)特別対談
レインウェアのメカニズムや使いこなしについてさまざまな論点が出されました。この対談で提示された疑問がそのままラボのリサーチテーマになっていったと言っても過言ではありません。

#2レインウェア・マーケット分析
市場に存在するレインウェアを多角的に分析し、利用シーンをもとに分類しました。超軽量レインウェアとウインドシェルが用途的に重複するのではという発見もありました。現在では古くなった製品も含まれていますが、この分類軸は未だ有効であると思います。

#3 透湿試験とメンブレンの解説
メカニズムと既存の試験方法について深掘りしました。「疎水性」「親水性」というキーワードが重要性をおびるとわかるのはこの後、実際の実験結果がこの両者で大きく異なることに気付いてからです。

#4 独自検査法による透湿性能試験
ムレた高湿条件での透湿性をはかるべくオリジナルの調査を実施しました。結果にバラツキはあったものの、疎水性素材の優秀さと、ゴアテックスの保温性というメリットが浮き彫りになりました。

#5 電子顕微鏡による組成解析
謎の多い各社の素材をハダカにすべく、電子顕微鏡でアプローチしました。これまでの仮説を深めることができました。

#6 これまでのまとめ
#1~#5までのまとめです。こちらを一読いただければこれまでの流れがわかるようになっています。

#7 同一試験による防水透湿素材の総合評価
レイン素材単体の総合的なレビューです。実験結果をもとに、「疎水性」「親水性」を軸として素材を整理しました。透湿性や保温性、軽量性を高次に満たす完璧な素材はありませんでしたが、総合点のよい高バランスの素材をいくつか特定することができました。

#8 レイヤリングのもたらす効果
レイン素材をレイヤリングした場合の効果をテストしました。メリノウールの優秀さと、速乾をうたっていても蒸れやすいという化繊の弱点が明らかになりました。山と道レインもレイヤリングにはメリノウールを強くおすすめします。

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Size

Recommended Size

Unisex
Size XS S M L XL
身長
(Height)
cm
150~161 159~167 165~175 173~180 178~185
体重
(Weight)
kg
42~53 51~61 59~69 67~78 76~85
ウエスト
(Waist)
cm
60~70 68~80 74~84 82~92 90~94

Product Size

Unisex
単位:cm
Size XS S M L XL
パンツ丈 102 105.5 109 112.5 115
股下 75 78 81 84 86
ウエスト 66 71 76 81 86
ヒップ 53.5 55.5 58.5 61.5 64
裾巾 10.7 11.7 12.7 13.7 14.7

Please Note

  • The UL Rain Pants are our ultralight water-resistant rainwear made of ultrathin, water-permeable fabric. Please handle with care as it can be torn or ripped when rubbed against rocks or scratched by spiky branches.
  • The UL Rain Pants are comfortable when you on the move in a relatively warm environment. However, they are less warm than normal water-resistant pants or winter hard shell pants so we strongly recommend you wear a merino wool base layer to keep you warm especially when severe weather is to be expected.
  • In order to maximize the moisture-permeability of the UL Rain Pants PU Sosui/Shinsui, after-use care is necessary. The performances of the membrane, facing and lining can be impaired by dirt, sweat, and skin oil, or other substances. Please follow the washing instruction of each product to properly wash, dry, and keep them clean. The use of rainwear-specific detergent is highly recommended.
  • We recommend the use of water repellent spray regularly to restore the water repellency of the fabric.
  • The PU Sosui uses ultralight and thin microporous material, the Pertex Shield Pro. Vaseline, insect repellent, and ethanol-containing substances such as hair creams, cosmetics and sunscreens may stain the fabric. They may also hinder the water-permeability of the fabric. Please visit the following link to remove the oil stains:山と道JOURNALS『山と道修理部通信#2 レインウェアの油脂汚れをきれいにする』
  • Because the Pertex Shield has a different moisture permeability mechanism, the PU Shinsui is not stained by Vaseline, etc.

Care Insructions

  • Machine wash, gentle at 30°C.
  • Use rainwear-specific detergent if available.
  • Wash separately or use a laundry net bag.
  • Fasten the zipper before washing.
  • Tumble dry below 60°C.
  • Do not bleach and do not use fabric softener.
  • Iron on low, covered the pants with a cloth. Do not steam.
  • Do not dry-clean.

Payment

  • We only accept payment by credit card. We currently do not accept payment via bank transfer from overseas accounts.
  • We accept the following Credit Cards: Visa, Master, American Express, and JCB.
  • To download your receipt, please click the link included in the Dispatch Notice, which we will send by email as soon as the items are dispatched.

Delivery

We will ship by DHL for overseas customers (excluding China and Russia). For customers in China and Russia, we will ship by EMS only. Shipping costs vary depending on your country and region.

Size Exchange

  • Overseas customers who need to change the size of their order, should note that the time needed for shipping will vary greatly depending on your country of residence.
  • We only accept exchanges when the item is unused (except for fitting).
  • If you wish to exchange the size of the item, please contact us within seven days of receiving your order.
  • Exchanges can only be made for the same color in a different size.
  • If the size you wish is out of stock, we will suggest a different color.
  • If the product is out of stock, we may simply have to ship the item back to you.
  • All shipping costs to be carried by the customer.
  • We will only send the exchanged item to you, upon receipt of return shipping cost via PayPal.
  • Please be aware that some countries charge customs duties depending on the price of the item.
  • We are unable to answer any questions on local customs. Please contact your local customs bureau.

Repair

We accept repairs for all of our Yamatomichi products. For inquiries on repair services including patching the holes, repairing with extra components, or fixing the items damaged over time, please feel free to contact us from the “Repair” section of the SUPPORT page.

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