Aquaseal for caving equipment protection, repair, and construction

by John Ganter

McNett Aquaseal (1) is a tough, flexible, and waterproof urethane sealant. It sticks to leather, neoprene, nylon, aluminum, and PVC. AquaSeal is very abrasion and cut resistant. It is excellent for protecting the toes and seams of leather boots, seams of coveralls and packs, and high abrasion areas like knees and elbows. It can also be used to attach patches or pockets of virtually any fabric.

Aquaseal in 1 and 8 oz sizes (McNett photo) TubesOfAquaseal.jpg (17k bytes)

Aquaseal resembles the "GOOP" and "Shoe Goo" sealants that are widely available, but it is much tougher and longer lasting. Compared to Aquaseal, GOOP bonds poorly to leather and coated fabrics, and water weakens it quickly. GOOP also tends to dry out, turn yellow, and crack.

Aquaseal contains toluene, a nasty, volatile solvent. The toluene penetrates the base material (leather, nylon) thus carrying the sealant beneath the surface. The toluene then evaporates during the polymerization process, which takes about 24 hours. The McNett spec sheets say that Aquaseal is 78% rubber, and it darkens and stiffens fabrics significantly.

While curing, Aquaseal remains runny, so try to level the item being sealed and protect anything that might get dripped on. If Aquaseal gets onto something, it is hard to remove either wet or dry. You can clamp patches by covering the Aquaseal with thin, slippery foam or plastic wrap and then placing bricks or other weights on top.

When using Aquaseal, wear a cartridge respirator and gloves. The cartridge should be effective against organic solvents. Since toluene is absorbed by the skin and eyes, working outdoors with a fan is recommended. Take care of your central nervous system; they are hard to replace!

Seamgrip is a thinner form of Aquaseal (2). It penetrates seams better and may be better for gluing fabric together.

For super penetration of boot leather, Aquaseal can be thinned by half with toluene. Boots that are given several treatments of this mixture are very resistant to wet, high abrasion caving, report Mike Ficco and Ben Schwartz. See the NSS News, September 1999, for photos!

Seams, coating, and masking

Caving suits usually have many exposed seams, and these are areas of vulnerability. Aquaseal can protect them. The quickest technique is to just run the tube down the seam and then spread the Aquaseal around with a gloved finger. And you are wearing your respirator, right?

A neater technique is to mask the seams. Masking can also be put around a knee or elbow patch (see photo below).

Aqua_Mask_(Sfw64104_03).jpg (16754 bytes) This elbow patch on a Helix caving suit is being coated with Aquaseal for abrasion resistance. Masking tape is being used to keep the Aquaseal from running all over the suit.

Let the Aquaseal dry for 2 hours. At this point it will be soft, but not as runny. Peel off the tape (see photo below). You can also add a sprinkling of sand so that the Aquaseal is not as slick. This is good for knee and elbow patches, since you need good grip while climbing and chimneying.

Aqua_MaskAndSand_(Sfw64104_05).jpg (31413 bytes) Peeling masking tape from around an elbow patch after two hours. A sprinkling of sand has been added for friction.

Result: This patch is very stiff. I will use less Aquaseal and sand next time.


Caving is very hard on boots, particularly the toes. They are loaded with your body weight, and then stuck down in rocks, mud, and water. Aquaseal can provide a lot of protection.

The minimal treatment is the toes. Tilt the toes up, mask the sole, and put on the Aquaseal. Did I mention the respirator?

A more advanced treatment protects the sides and uppers also. This is worthwhile for a good pair of boots that will be used in heavy abrasion.

Since Aquaseal is so runny, I have found that the best way to do a full coating is in two halves (photo below). Mask the sole and the lacing. Now run masking tape down the midpoint of the toe and heel. Coat away.

Aqua_BootOnSide_(Sfw64104_06).jpg (19478 bytes) Masking the sole. You can see that this boot already has some Aquaseal on the toe and side seam, but now the leather is starting to abrade and it needs more protection.

It's best to do both boots at the same time (photo below). Let dry. Now, mask the dry Aquaseal, and do the other side. If you apply the masking tape with care, you will get a nearly-invisible seam down the toe and heel of the boot and unbroken Aquaseal everywhere else.

Aqua_BootsOnSide_(Sfw64104_07).jpg (18288 bytes) Coating the sides of a pair of boots. The masking leaves a nearly-invisible seam down the toe and heel.

After wearing and hosing these boots down a couple of times, I've concluded that they are heavily-armored, yet still flexible. They may actually last until the soles are worn out.


Aquaseal can be applied to wear-points on packs, or used to coat whole areas that are wearing through. I had a large Caving Supplies PVC pack with some existing Aquaseal patches (see photo below). Now the whole thing was on the verge of wearing through.

Aqua_PackPvc_(Sfw64104_10).jpg (18660 bytes) A well-worn Caving Supplies PVC pack. The pack is being masked in preparation for Aquaseal. Arrow indicates test area for Liquid Electrical Tape.

For the edges of the pack, I wanted a super-thick coating of Aquaseal. This is hard to do, because of the runniness and the fact that Aquaseal does not stick well to cured Aquaseal. Here is what I did.

I applied one coat, let it dry for two hours, added another coat, then removed the masking at 4 hours total elapsed time. This let the first coat dry somewhat, but it was still wet enough for the second coat to adhere to it. The masking tape was still removable after 4 hours.

I also left a small island (arrow in photo) that I gave three coats of Liquid Electrical Tape for a side-by-side comparison with Aquaseal.

Test results: I did a couple of mostly dry trips and both coatings were holding up well. Then I did a 13 hour trip with the pack heavily loaded and dragged through water and on rock and gravel. There was 150 feet of low-airspace crawl on the way in and out, so the pack was wet and abraded most of the time. The Liquid Electrical Tape is cut deeply, and is peeling off in several places. The Aquaseal is no longer shiny.

Adding a pocket with the contact cement technique

Aquaseal can also be used to construct patches and pockets. I added an inside pocket to the Helix suit. Since the inside of the suit is coated, the first thing I did was sand the coating to roughen it.

Then I used the "contact cement" technique. This helps to control where the cement runs, and allows heavy weighting of the joint. Here is how contact cementing is done:

  1. Coat both items to be joined with the cement (Aquaseal, or maybe Seamseal is even better). Work the cement in well. But don't join the two items yet.
  2. Now, let the two items dry for awhile. You want them to be very tacky. I recommend one to two hours for Aquaseal.
  3. Press the two items together. Add weights or clamps.
  4. Allow to dry completely.

This is how I did the pocket (photo below).

Aqua_Pocket_(Sfw64104_20).jpg (33174 bytes) A pocket added to the inside of a Helix oversuit with Aquaseal. Arrow indicates heavy coating of Aquaseal at the corner, which acts like a bar tack.

I also added a patch of Velcro to keep the pocket closed. Contact cementing Velcro is tricky. It is important to keep Aquaseal from leaking onto the hooks or loops. It is probably best to use a very thin coating on each tape, then weight them together with some plastic wrap between them. After drying, touch up the edges of the Velcro with a little Aquaseal.


Aquaseal is a remarkable coating and adhesive. If your time is very valuable, it may be more cost-effective to discard or donate worn gear rather than doing major coating projects. But often a little bit of Aquaseal makes a big difference, especially on boot toes.


You can get Aquaseal from some marine and dive shops, and reportedly from REI. The large tubes are most practical for coating, and much more economical.

Divers Supply (1-800-999-3483, has the best single-tube Aquaseal price that I have found. A 1 oz. tube is $5.95, an 8 oz. tube is $17.95.

Outdoor Wilderness Fabrics (208-466-1602, sells Seamgrip for $19.32 and Aquaseal for $19.50 in 8 oz. tubes. These prices drop significantly if you buy more than $50 worth of items.


Version 1 appeared on Cavers Digest 5623, 29 June 1999. Chuck Porter added several items when he printed version 2 of this article in the Northeastern Caver, Sept. 1999. Thanks to Ben Schwartz, Mike Ficco, Ron Simmons, Duke McMullen, and Mark Minton for contributing information.


(1) McNett sells several urethane sealants, including Aquasure for waders and Megathane for camping and home use. I would guess that they are all either Aquaseal (thick) or Seamseal (thin) aimed at specific markets. I called the GOOP company a few years ago and they confirmed that all the GOOPs are exactly the same, just packaged differently so they can hang in the auto, plumbing, etc. section of the store.

(2) In version 2 of this article I reported incorrectly that Seamgrip was thicker than Seamseal. It is actually the opposite.

Version 3, 2 & 15 November 1999



WB01727_1.gif (697 bytes)
BallBlue.gif (954 bytes) Caving Technology Website home BallBlue.gif (954 bytes) Copyright and Disclaimer BallBlue.gif (954 bytes) Feedback

visits since 18 October 2003