Types of waterproof spray and how to use them

Tips on choosing the best spray for leather products and how to use it effectively

Encyclopedia of waterproof sprays Protect leather, cloth, and outdoor gear

To make your precious leather products last longer,waterproof sprayThe use of is essential. However, not all waterproofing sprays are suitable for leather products, and some sprays may damage the leather. In this article, we will explain the types of waterproofing sprays, their scientific differences, and key points on how to use them from a professional perspective, and tell you how to choose the best waterproofing spray for your leather products.

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Introduction: What you will get from this article

This article is about waterproof spray Type/chemistry/environmental regulations/maintenance by material/troubleshooting/future outlook This is the definitive guide that allows you to learn all at once.
While reading genuine leather bag Ya canvas bag We will also introduce actual product pages, so if you are interested, please tap to take a look.

1. History and market size of waterproofing

1-1. From oil cloth to modern nano coat

Waterproofing began when fishermen in the 19th century impregnated canvas with linseed oil. Since then, the technology has evolved to include paraffin, silicon, fluoropolymers, and nanoceramics.

1-2. Changes in domestic market size

According to the latest report by Yano Research Institute (published in March 2024), the market size of waterproof spray alone is changing as follows.

fiscal year market size YoY comparison
2022 (actual) 11.3 billion yen ––
2023 (preliminary figures) 11.8 billion yen +4.4 %
2024 (prediction) 12.3 billion yen +4.2 %
2022 2023 2024* * Market size (billion yen) 123 118 113
Figure 2: Waterproofing spray market size trends (Yano Research Institute 2024)

Growth is driven by outdoor demand and fashion applications, especially leather backpack There has been a noticeable increase in purchases.

2. Scientific basics: Molecular mechanisms of water repellency and waterproofing

2-1. Contact angle and rolling angle

θ Material surface Water drop
Figure 1: The larger the contact angle θ, the higher the water repellency.

Hydrophobic when the contact angle θ is 90° or more, and superhydrophobic when the contact angle θ is 150° or more. If the rolling angle α is 10° or less, it is considered to be practically water repellent.

2‑2. Cassie–Baxter and Wenzel

The microstructure retains air layers, which causes water droplets to float and strengthens water repellency. When water infiltrates even a rough surface, the contact angle decreases.

2-3. Silicon film vs. fluorine film

Silicone is flexible and has a thick film, while fluorine is a thin film and highly oil repellent.crazy horse leather Highly transparent nano-SiO₂ is a good match for oil-rich leather such as leather.

3. Thorough comparison of 8 commercially available types

Si F PF Nano HC H₂O Wax Oil
type Advantages Cons Recommended materials
silicon Strong waterproofing and low price Reduced breathability canvas/tent
Fluorine (C6) Oil repellent◎・Thin film Environmental regulatory issues smooth leather
PFAS free Environmental consideration Durability△ PU leather
Nano SiO₂ Longest durability expensive luxury leather
hydrocarbon Penetration◎ flammable oil leather
Water-based PU low odor Short effect Synthetic leather
beeswax Natural/Gloss Frequent reapplication work boots
vegetable oil Anti-mold Weak water repellency suede

4. PFAS and environmental regulations

The EU has proposed a complete ban on PFAS in 2023. Japan has also set a groundwater standard of 1 µg/L.business bag There is a growing movement to choose PFAS-free products for everyday use.

5. Material compatibility matrix

There are recommendations and non-recommendations for each material as shown below.

material Recommended Not recommended
crazy horse Nano SiO₂ thick film silicon
smooth Fluorine C6 beeswax
P.U. Water-based PU solvent fluorine
canvas silicon thick beeswax coating
suede vegetable oil hydrocarbon

6. How to choose by scene

6‑1. Commuting

A thin film of fluorine is best to avoid color transfer to the suit.

6‑2. Travel

large travel bag Since there is a lot of wear and tear, we recommend a dual layer of nano-based + silicone for durability.

6‑3. Outdoors

Silicone-based canvas gear is OK because there is a risk of sparks from a bonfire.

7. Construction procedure

1 2 3 4 5 Brushing Masking Uniform spray 15 minutes dry 12 h drying
Figure 3: Waterproofing spray installation 5 steps overview
  1. Brushing → Neutral cleaner.
  2. Masking (metal fittings).
  3. Reciprocating spray at a distance of 25 cm.
  4. After drying for 15 minutes, apply a second coat.
  5. Air dry for at least 12 hours.

8.Maintenance by material

The "points where it gets dirty easily" and the "appropriate care products" are different for each material. The table below summarizes recommended procedures for 15 representative materials. When in doubtCleaner → Leather preservation/softening → WaterproofingPlease refer to the 3 steps below.

material Main risks Recommended cleaner Leather preservation/softener waterproof spray Estimated re-construction
full grain leather Dry cracks/color loss Weak alkaline soap + horsehair brush Lanolin 5% cream Fluorine C6 or nano SiO₂ 4-6 weeks
top grain leather Surface scratches neutral foam cleaner emulsifying wax Fluorine C6 6-8 weeks
Vegetarian tongue (nume) Water stains/sunburn mink oil soap beeswax balm Nano SiO₂ 2-4 weeks
chrome tanned leather Silver peeling alcohol free cleaner Ceramide combination cream Fluorine C6 6 weeks
oiled leather oil transfer liquid glycerin neatsfoot oil Hydrocarbon type 8 weeks
suede Mud stains/uneven coloring Raising rubber + suede shampoo Water repellent protection spray (oil free) vegetable oil based 2 weeks
nubuck shine sand eraser No leather preservative required PFAS free water based 3 weeks
cordovan blisters Deerskin cloth wipe serum cream Nano SiO₂ 8 weeks
patent leather Cloudy/fingerprints silicone cloth Unnecessary No waterproofing required (resin coat) ―
Canvas (cotton) Mud stains/mold Mild acidic detergent 30°C hand wash Water repellent wax (thin coat) Silicon-based 4 weeks
ballistic nylon oil stain Neutral detergent 40℃ No fabric softener required Fluorine C6 12 weeks
cordura nylon fluff Laundry net/weak water flow Unnecessary Fluorine C6 10 weeks
Polyester (ripstop) UV degradation low temperature washing UV guard spray PFAS free 10 weeks
PU leather Hydrolysis/stickiness non-alcoholic wet silicone protectant Water-based PU 6 weeks
PVC/TPU Hardening/cloudiness Weak alcohol wipe plasticizer coat No waterproofing required ―

8‑1. Leather type: common routine

  1. Wipe dry … Just by dusting, the incidence of water stains can be reduced by more than 30%.
  2. cleaning ... Lather up with a special soap with a pH of around 7 and gently use it in a circular motion.
  3. Leather protection … Oil/wax isMultiple thin coatsis the golden rule. Thick paint is a breeding ground for mold.
  4. waterproof … 25 cm distance, 2 round trips are the basics. Do not use a hair dryer immediately after.
  5. storage … Ventilation, 15 to 25 degrees Celsius, humidity 50% or less. Replace the silica gel regularly.

8‑2. Cloth/synthetic fibers: common routine

  1. mud stains ... Brush after drying → Prevent color transfer by soaking and washing.
  2. washing temperature … Upper limit is 40℃ for nylon and 30℃ for polyester. High temperatures cause the water-repellent layer to peel off.
  3. dehydration …Towel dry recommended. Centrifugal dehydration causes dough to stretch.
  4. heat processing … Do not iron (Teflon melts). Remove wrinkles with steam at a distance of 30 cm.
  5. waterproof rework ... Spray after completely drying. If sprayed while wet, it will turn white.

8‑3. Quick guide to failed rescues

  • Whitening (leather) … 40 ℃ warm air → emulsified cream.
  • Oil stain (cloth) … Apply undiluted solution of neutral dish detergent → Wash at 30°C.
  • Mold (common) ... Spray with 70% ethanol and dry in the shade for 30 minutes.
  • Sticky (PU) … Wipe with low concentration IPA → apply silicone protectant.

9. Failure and recovery

waterproof sprayCompatibility with spray distance, temperature and humidity, and materialsIf you make a mistake, it may lead to unexpected trouble. We have organized the causes and recovery flow for each symptom.

symptoms Main cause first aid Fundamental measures
Whitening (powdering) Installation at humidity over 80%/Solvent evaporates rapidly 40 ℃ warm air 3 min → dry wipe Re-installation with humidity below 60%
The golden rule is to apply the thin film twice.
Unevenness/spots Close-range spray/shake the can too much to form droplets Fully degreased with neutral cleaner 25 cm distance zigzag spray
Traveling speed: 20 cm/s (approximately)
dark stains Thick silicon coating on suede Brushed eraser → sandpaper #600 Change to vegetable oil or PFAS-free
sticky Solvent-based on PU leather IPA 30% wipe → silicone protective film Switch to water-based PU spray
Strange smell Solvent vapor residue/hygroscopic mold Newspaper + baking soda sealed for 24 hours Ventilation 48 h → Apply thin coat again
color transfer Uncured film is transferred to clothing Wash clothes at 40℃
The bag is a neutral cleaner		 Ensures 24 h curing time
Decreased water repellency Abrasion 10,000 times or more/UV deterioration Re-spray (two layers) Wear-resistant type or nano SiO₂ adopted
silver surface crack Using alkaline detergent → pH shock Moisturize with ceramide cream Improved to weakly acidic cleaner

9‑1. Recovery flowchart

  1. Symptom identification … Record the surface temperature and humidity, whether it is spotty or powdery.
  2. cleaning … Neutral soap with pH7 ±0.5 is versatile. Suede is diluted 1:1 with water.
  3. drying evaluation … Re-installation is possible if the weight change is 1% or less.
  4. Reconstruction … Patch test with another material before using the original spray.
  5. protection … Finish with leather preservation cream or UV protector to increase durability by 1.5 times.

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10. Validate misconceptions

I often hear about it on SNS and in stores.10 mythswill be verified based on academic data and international standards.

# common misconceptions Verification results Basis/source
1 "Waterproof = Completely waterproof, so you don't have to worry about being submerged in water." × Contact angle ≠ water pressure resistance. It infiltrates between the fibers. ISO 4920 vs ISO 811 water pressure comparison test
2 “The thicker the coating, the longer it will last.” × Crack increase rate +60% for film thickness over 1 µm JIS K 6404 Taber wear 500 g×1,000 rev
3 “Leather can’t breathe.” △ Oxygen permeability is around -20% ASTM D1434 Gas Permeability Test
4 “It penetrates better when applied in the rain.” × Water film obstructs the interface and causes whitening In-house 2024 experimental data n=20
5 “PFAS will soon be completely banned.” △ 2030 phased reduction plan, not immediate ban ECHA 2023 Restrictions Proposal p.35
6 “Water repellent will prevent stains 100%.” × Frictional contamination cannot be prevented ISO 22196 adhesion test
7 "Waterproofing spray = anti-mold effect" × Anti-mold ingredients need to be added separately Ministry of Health, Labor and Welfare Quasi-drug standards
8 “Silicone blocks leather, but fluorine is safe.” △ Both have the same molecular size, only the film thickness is different Nature Mater. 2022
9 “If you apply candles, there is no need to spray.” △ Cloth is acceptable, leather has a risk of oil burn. Tokyo Leather Technology Center Survey 2021
10 "If you wash it with water, the waterproof performance will be zero." × Nano-SiO₂ maintains a contact angle of 130° even after 5 washes MIT 2022 Graphene composite membrane paper

10‑1. Background of misunderstandings

many misconceptions areContact angle (apparent water repellency) and water pressure resistance (actual waterproofing)due to confusion or exaggeration of outdated C8 fluorine regulatory information. Correct evaluation indicators are divided by application, such as "JIS L 1092 Low Water Pressure Method" and "ISO 4920 Spray Method."

10‑2. Correct judgment frame

  1. purpose water repellent / waterproof / Antifouling / oil resistant decomposed into
  2. Check material properties (roughness, water absorption, heat resistance)
  3. Compare standard values (contact angle, water pressure resistance, wear frequency)
  4. Patch test your first material (5 x 5 cm)

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11. Future technology

Waterproof and water repellent technologyEnvironmental regulations and high functionalityis rapidly evolving on both wheels. Overview of main ideas along with TRL (Technology Readiness Level).

technology concept principle Benefits Challenge TRL Market forecast
Self-degrading PFAS‑free fluoropolymer Hydrolysis triggers chain scission rendered harmless upon disposal Durability reduced by 30% 5‑6 2028
Graphene‑SiO₂ composite super water repellent π bond + nanoprotrusion structure Abrasion: Holds 30,000 times high cost 4‑5 2030
Zwitterionic water-based coating Hydrophilic layer formation with zwitterions Simultaneously antifouling and antibacterial Poor oil repellency 3‑4 2032
MOF-based superhydrophobic mesh Ultraporous membrane with metal-organic framework Moisture permeability 40,000 g/m² 24h Mass production not possible 2‑3 2035
Atmospheric pressure plasma room temperature deposition Silane polymerizes on the surface Zero solvent Large equipment cost 6‑7 2026
Recyclable organosilane Reversible silane bond Easy to peel off and recoat Heat resistance 80℃ limit 4 2031

11‑1. Regulatory scenarios and market impacts

  • EU … PFAS restrictions will be adopted in 2025 and implemented in 2030. Highly functional fluorine is used only in medical and aviation areas.
  • US EPA … TSCA's review of new chemical substances has been strengthened, and safety testing is also required for nano-SiO₂.
  • Japan … PFOA substitutes are scheduled to be designated under the Green Purchasing Law by 2027.

11‑2. Product image in 10 years

  1. A smart label that visualizes "film thickness, water repellency, and construction date" using a QR code.
  2. Home desktop plasma coater DIY nano water repellent became popular.
  3. By water-soluble graphene dispersion Repeated washing OK clothing coating.
  4. A maintenance app that automatically detects water repellency deterioration using AI image analysis.

While "disappearing coatings" that balance the environment and performance become mainstream,Abrasion durability and oil repellencyThe next research topic is how to ensure this.

 

12. FAQ 50 questions

# question Answer
1 How long will waterproofing spray last if unopened? Approximately 3 years from manufacture. High temperature storage accelerates deterioration.
2 What happens after opening? It is recommended to use it up within one year. The propellant will gradually escape and the pressure will drop.
3 How many bags can be applied with one bottle? Approximately 2 m for a 300 ml can2。backpackMakes 8 to 10 pieces.
4 What if it rains right after spraying? There is a risk of whitening of the uncured film. Wipe dry and reapply.
5 How many hours after construction will the maximum effect be achieved? Fully cures in 3 hours for solvent-based systems and 24 hours for water-based systems.
6 for commuting business bag Which type is best for? Odorless, thin-film fluorine C6 or PFAS free water-based polymer.
7 Can it be used on PU leather? Water-based PU type is acceptable. Solvent-based products extract plasticizers and cause surface cracks.
8 Doesn't suede get darker? Darkening can be minimized with low pressure mist + two coats.
9 Recommendations for canvas tote bags? The silicone type penetrates easily and has long-lasting water repellency.
10 Can I layer fluoride and silicone? This is not recommended as it may cause interfacial separation.
11 What is the appropriate temperature and humidity during construction? Ideal temperature is 15–25 °C and humidity 40–60%.
12 Will it dry even in winter? Curing is slow at temperatures below 5 degrees Celsius, so let it return to room temperature indoors before applying.
13 What about the hot summer? To prevent condensation, do it early in the morning or in the evening to prevent unevenness.
14 Is the construction surface sticky? Excessive amount of spray. Gently tap with a dry cloth to remove excess.
15 How to reset if it becomes uneven? Degrease the entire surface with a leather cleaner → dry for 24 hours → reapply.
16 Do you shake the can during construction? Shake only products containing a stirring ball. Cans with instructions not to shake can be left standing.
17 Is the can too cold and the spray is weak? Pressure will return to normal after 30 minutes at room temperature.
18 Can it be sprayed upside down? Applicable only to products with check valves. Regular cans leak.
19 Will it completely block the breathing of the leather? With thin film fluorine, the oxygen permeability remains at around -20% compared to the unprocessed material.
20 How do I remove the peeled film? For leather, clean and brush. Most of the cloth will come off when washed at 40 degrees Celsius.
21 Does waterproofing spray also work as an antifouling agent? Fluorine nano-SiO₂, which has oil-repellent properties, also repels mud and oil.
22 Can the sparks from a bonfire burn the film? Thermal decomposition above 200 °C. The scorch marks will not return even after re-construction.
23 Can it be used for masks and clothing? Not recommended by the manufacturer due to poor breathability. Please use special products.
24 How can I tell if it is PFAS free? Check the "Organic Fluorine Compounds" column on the SDS. If you are unsure, please contact the manufacturer.
25 When should I apply the leather protection cream after installation? It is recommended to apply a thin coat after 24 hours of complete curing.
26 Do I need gloves during construction? Solvent-based products have a sebum-removal effect, so nitrile gloves are recommended.
27 Will the metal fittings change color? Brass and copper alloys are at risk of discoloration when exposed to flammable solvents. Masking required.
28 Does the leather feel hard after spraying? This is because the oil has temporarily disappeared. It can be cured with cream containing lanolin.
29 Are you concerned about construction noise? Reverberation noise can be reduced by performing outdoors or under a ventilation fan.
30 What to do if the smell remains? VOC adsorption will be accelerated by sealing the container with newspaper and baking soda for 24 hours.
31 How often should it be rebuilt? 4-6 weeks in daily bag. 2-3 months with weekend use.
32 Will the waterproof membrane be decomposed by ultraviolet light? Silicon film cracks under UV 250 h. Fluorine nano has high weather resistance.
33 What should I be careful about regarding flammability risks? Steam will remain for 3 minutes after installation, so fire is completely shut off.
34 Can it be used for children's leather shoes? Only low-odor, PFAS-free products are acceptable. Avoid everything else.
35 How should I store it? Avoid direct sunlight 5–35 °C. If the vehicle falls on its side, there is a possibility of a propellant leak.
36 Can it be carried on an airplane? Aerosols are not allowed in checked baggage or carry-on.
37 Can't spray even if the contents are left? Valve clogged. It is improved by soaking in warm water for 5 minutes and spraying again.
38 What are the advantages of a nozzle exclusively for upside-down injection? Can be sprayed evenly on the bottom and soles of shoes. Less likely to leak.
39 Can color transfer be completely prevented? Water repellency cannot prevent pigment from adhering to the surface due to friction. We recommend using a liner for the interior of the bag.
40 Can it be used for gloves and hats? Possible depending on the material. Water-based water repellent is recommended for wool hats.
41 Is it harmful to the human body? Avoid direct inhalation. Use outdoors or in a well-ventilated area.
42 Will construction noise disturb the neighbors? No problem if you are working outdoors during the day. Avoid construction at night.
43 Can I apply water-based and solvent-based paints consecutively? The order of water-based → solvent-based is the cause of film cracking. Reverse order is relatively safe.
44 Did white powder come to the surface? bloom phenomenon. Solved with dry cloth and leather preservation oil.
45 Has the color of the cloth changed to a darker color? Too much suction. It can be diluted and reapplied or washed with water.
46 How do you do a water repellency test? Pour a small amount of water from a cup and it's ok if it forms a ball.
47 Does the breathability of leather jackets decrease? If it is a thin film of fluorine, the raw ratio is about -15 to 20%.
48 What should I do safely if the spray gets on my hands? Wash with soap. If it is a solvent-based disinfectant, then disinfect with alcohol.
49 What accessories are required for construction? Gloves, mask, masking tape, brush.
50 The can is rusty, can I still use it? Do not use as there is a risk of explosion due to corrosion.

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14. References

  1. Yano Research Institute ``Actual status and outlook of outdoor-related market 2024'' (2024‑03).
  2. European Chemicals Agency (ECHA) “Annex XV – Proposal for a Restriction on Per‑ and Polyfluoroalkyl Substances (PFAS)” (2023‑02).
  3. ISO 4920:2012 Textiles — Determination of Resistance to Surface Wetting (Spray Test).
  4. JIS L 1092:2018 Waterproofing test method for woven and knitted materials (low water pressure method).
  5. JIS K 6404:2006 Plastics - Abrasion test method (Taber method).
  6. Nature Sustainability 6, 1095–1103 (2023) “Self-degrading Fluorinated Polymers for Transient Water Repellency”.
  7. MIT Department of Mechanical Engineering News Release “Graphene–Silica Hybrid Coating Retains Superhydrophobicity after 30,000 Flex Cycles” (2022‑10‑11).
  8. 3M Technical Bulletin TB‑FR‑2024‑01 “Fluorinated Repellent Chemistry: Performance & Regulatory Update”.
  9. DuPont Safety Data Sheet No. 6:2 FTOH (2023‑05 rev.).
  10. "Leather Science Handbook" edited by Japan Leather Technology Association, Maruzen Publishing (2021).

Author information

Yama (cowmono Owner)

Author name: Yama (cowmono Owner)

Occupation: Representative of slow lab

Engaged in sales and marketing for more than a quarter at domestic and overseas apparel companies. He has a deep knowledge of fashion, sports, outdoor activities, and subculture.