Features July 2011 Issue

What's the Best Way to Clean Rope?

Practical Sailor tests suggest that some common practices for cleaning ropes do more harm than good

hotos by Drew Frye

Pillowcases could not protect some ropes from the rigors of machine washing.

Every spring, there are numerous threads on the sailing forums discussing the best ways to clean ropes, mostly about dock lines. Brutal methods are suggested: power washing, soaking in a bucket of bleach for a week, scrubbing them with Spick-N-Span and leaving them on a bright concrete sidewalk to dry. Others recount experiences of ropes disintegrating in their washing machine, of washers being mangled, and adamantly insist that the only safe method is gentle agitation in a tub with the lightest touch of Woolite.

Our own interviews with technical representatives from major rope manufacturers Bluewater Ropes, New England Ropes, Samson Cordage, and Yale Cordage on this topic yielded uniformly conservative guidance. These makers have all faced claims of rope failure resulting from poor cleaning methods. They all recommend some cleaning, but they generally suggested this should be limited to a freshwater rinse. Rinsing removes salt crystals and is safe, even for an obsessive-compulsive rope-cleaner. The truth is that mildew and algae don’t weaken synthetic ropes, so cleaning green stains from your jib sheets is a purely cosmetic effort. Generally, anything but a mild rinse is best avoided for the first few years in the life of your running rigging.

Advice from makers

In search of definitive guidance on rope cleaning (see “How We Tested”), we turned first to manufacturers for advice. Although the advice varied in some details, all agreed on the following points.

Wash only with a very mild detergent. For relatively new ropes, this means something like Woolite or a half-dose of a modern laundry detergent. For the first few years, ropes still contain thread coatings and lubricants from the factory that provide an easy hand, as well as offer some protection from UV radiation, abrasion, and water absorption. Washing a new rope in a cleaner touted as degreaser will harm this protective coating. After several years, when these lubricants have clearly been washed away by rain and worn off by normal use, ordinary laundry detergents at ordinary doses are acceptable. Avoid any cleaners that have a pH value below 7 or above 9, exaggerated soaking periods, or exaggerated doses. Most common laundry detergents are buffered in this pH range when used as directed.

Wash on the gentlest cycle. The rope should be tightly coiled or tied in a daisy-chain, and then placed inside a pillowcase. Front-loading washing machines are recommended; an up-and-down motion is preferable to the rotary motion of most common household machines. Without coiling or daisy-chaining, a rope can turn into an impressive tangle. The pillowcase further restricts the motion of the rope and prevents the rope from wrapping around the central agitator, which can destroy ropes and break washing machines. For a video of daisy chaining, search “chain sinnet” (also called a monkey braid), on www.animatedknots.com.

Avoid contact with acids, bases, and solvents. Both polyester and nylon (polyamide) are vulnerable to certain chemicals, so manufacturers broadly warn against using them. However, both nylon and polyester are unaffected by most solvents. Extended exposure to certain alcohols can weaken polyester. Both nylon and polyester have some vulnerability to alkalis such as those found in strong cleaners like TSP (trisodium phosphate) or Spick-N-Span.

Nylon is particularly vulnerable to acid. Strong acids such as battery acid or muriatic acid can literally melt right through a nylon rope in a matter of minutes. Soaking for an hour in weak acid cleaners (typically based on phosphoric acid, oxalic acid, citric acid, or acetic acid) such as Lime-Away or Shower Power can weaken the rope by as much as 50 percent without any worthwhile cleaning benefits. Avoid all acid cleaners, including vinegar, and diluted acids.

Fabric softener at recommended doses is approved. However, high doses of fabric softener can weaken ropes, primarily because they prevent complete drying.

Power washing is not recommended. While it can be an effective method for cleaning marine growth from mooring pendants and dock lines, a power washer in the hands of an inexperienced operator can do significant damage. High-pressure water can easily cut through a line and do significant hidden damage. Power washing can be carried out safely by keeping the power-washer nozzle at a sufficient distance, but there is no easy way to tell whether your work is causing some hidden damage.

Bleach is not recommended by any manufacturer in any quantity. Every manufacturer has faced claims of rope failure or splice failure caused by a bleach overdose. Extended soaking in bleach solutions must be avoided.

Hot water is not a problem. Nylon and polyester are undamaged at normal water-heater temperatures (120 to 135 degrees).

Don’t dry with heat. The rope should be flaked loosely on the floor and left to dry. Nylon and polyester ropes are not typically heat-set, and there is great risk that the sheath and core will shrink differently, causing distortion and structural damage to the rope.

The following additional experience was volunteered by professional riggers:

Washing won’t make splicing easier. Old double-braid is difficult to splice, and washing doesn’t change that. Polyester remains too stiff even if treated with fabric softener.

Washing machines don’t like nylon double-braid. Nylon double-braid is subject to herniation and destruction during the machine-washing process. Never machine wash a new or nearly new nylon dock line!

Bleach is very bad (again). This one is worth repeating. Each spring, riggers are asked to re-do splices that have come loose after bleach ate the stitching and whippings that secured the splices. Without a few key stitches, a splice will be milked apart in 30 minutes of agitation.

1. This climbing rope is still neatly daisy-chained after washing. The rope has survived 10 careful washing/waterproofing treatment cycles over 15 years, with no apparent damage. 2. This used dock line failed at the splice, which was not whipped. 3. Splices secured with whipping survived; those without whipping did not. 4. This heavily encrusted rope is ready for the wash. It came out clean, after a pre-soak and gentle wash. 5. This new nylon dock line was destroyed by a gentle wash. A coiled twin of this sample came out even worse. 6. This photo shows a typical polyester line before and after bleaching. Notice how the stains were not significantly reduced.

What We Tested

Several hundred feet of decrepit dock lines were collected as part of a Chesapeake Bay area marina cleanup program; most of these lines had been in place for 10 to 20 years, strung between slips, abandoned by former owners and left hanging, or dropped to the bottom. Several hundred feet of used but good condition polyester, double-braid line (New England Ropes Stay-Set) were donated by a local rigging company. All of these lines were cut up into manageable lengths and subjected to a variety of machine cleaning methods.

Some were barely dirty, while others were nearly twice their original diameter, encrusted with all manner of marine life. While in some cases we were able to recover usable line from apparent trash, in many cases old dock lines simply disintegrated during cleaning. Polyester double braid was undamaged by any machine cycle, either visibly or by feel.

Our testing was limited to nylon dock lines and polyester double-braid. We did not perform strength tests on used lines because the histories were unknown, so the results would be of little value. We also washed several lengths of new dock line from New England Rope and Samson, as we were warned by riggers that these were particularly vulnerable to damage by machine washing. We also exposed new nylon double-braid dock lines to bleach for several fixed time periods. The ropes were then sent to New England Ropes, where they were load-tested until they broke to determine the effect of bleach on ultimate breaking strength.

This project was less about collecting scientific data than about collecting practical experience about what works and what doesn’t. We also got to spend hours practicing washing machine repair. Woo-hoo! That’s testing.

Practical Lessons Learned

Rather than drag you through the hours of testing and washing-machine repair that our test entailed, we’ll focus on what we learned. Here are the highlights:

Carefully whip or melt the end of every rope before washing. A few whippings came off, and the mess was impressive; three-strand line often unlaid to fuzz for several feet, until the first tight coiling restricted it. Double-braid fuzzed for at least a few inches. We also proved that this fuzz and bits could effectively jam a washing machine pump. Although a pillowcase reduces cleaning effectiveness, it prevents frayed bits of rope and heavy dirt from damaging the machine.

Pre-soaking allows more gentle cleaning. If the lines are heavily soiled with marine growth or algae, presoak them in a bucket of hot water with a regular dose of mild detergent for an hour. This is safe and very effective. Agitate by hand for a few minutes at the end of the soaking period, gently apply a scrub brush to the bad spots, and dump the water. This allows a much gentler cycle to achieve the same result, and the heaviest dirt is removed before placing the rope in the pillowcase, which reduces the amount of dirt trapped in the pillowcase during washing. Do not pre-soak with harsh detergents or bleach. These stronger cleaning agents are not needed and can cause significant damage.

Use the gentlest cycle that will clean the line. No used line was damaged when washed in the pillowcase, with ordinary detergent, on the gentle cycle. Washing clothes along with the pillowcase-enclosed lines helps protect the ropes during washing. The pillow will catch any heavy soil that might stain ordinary clothing. Extremely dirty ropes will have to be pre-soaked first.

Wire ties worked well for closing the pillowcases. None our test pillowcases came open. Don’t use your best pillowcases. They will take a beating.

Secure a sock over any spliced-on shackles. Secured with a wire-tie, a soft sock protects the shackle, rope, and washer.

Learn how to daisy chain your ropes. Ordinary coils frequently came apart, resulting in damaged ropes. Daisy chains fared better. The daisy chain should be slightly tighter than for ordinary storage; not tight knots, but not so loose that it shifts excessively during washing. Six-to-eight-inch loops worked well, depending on line size and stiffness.

Never machine wash new double-braid dock lines. New England Ropes double-braid failed by herniating the core through the cover every 6 to 12 inches within 10 minutes of washing, even on gentle cycle. Sampson Ropes double-braid dock line better withstood machine washing, but one of two eye splices failed (core pulled out of the splice). It’s the continuous back-and-forth milking of the cover in wet soapy water that causes the trouble, something a rope never sees in real use.

Some test ropes were thick with growth. Others were new from the factory.

Stitch all eye splices. Many eye splices survived, even on vigorous cycles. In all cases, the surviving splices were stitched to anchor the core and whipped at the join. All failures were un-whipped splices with no core anchoring stitches.

Be careful with soft-laid three-strand rope. Soft-lay, three-strand rope failed by hockling or unlaying unless washed gently in a pillowcase. Hard and medium-lay ropes faired much better. A scrub brush combined with gentle soaking is the safest method for heavily soiled dock lines. Labor intensive, but safe. Power washing blew some older ropes apart.

Polyester double-braid withstands machine washing very well. We were not able to visibly damage any quality polyester double-braid (Yacht Braid and Sta-Set) with any wash cycle or repeated washing—even uncoiled rope. This suggests that gentle washing of polyester running rigging is quite safe.

Avoid bleach (again). We tested the effectiveness of bleach by pre-treating with bleach and by bleaching after washing. In no case was a difference observable. If there is some minor mildew or algae growing on the tail of the rope, clean that portion of the rope, and set it in the sun. In our cooperative test with New England Ropes, it was found that bleach was aggressive in removing lubricants, roughening the texture of the line, and increasing stiffness, even when applied according to directions.

Acid cleaners are very damaging. We pretreated several lines with weak acid cleaners and saw no improvement; however, the lines were visibly softened and damaged, and had less than 50 percent of their original strength. Some have suggested that you need to use weak acids to remove lime deposits within the core, but there are lime removal agents (EDTA and triethanolamine) in most detergents, and these do the job safely. None of the ropes we washed had objectionable residual stiffness.

Rope cleaners aren’t worth the expense. We tested a purpose-built rope-washing devise by PMI, used by cavers and climbing schools to clean the grit out of muddy ropes. For the average sailing rope, the device was no more effective than a rinse with a hose.

Long-term findings. What about fabric softener, water repellents, and other rope treatments? We’ve found some very interesting products, but it is too soon to report on these. Durability of the treatments over time is critical, and we need time in the field to study them. Do they wash out in the rain? Do they negatively impact line clutch or winch efficiency? Do they help lines resist freezing and improve handling? We’ve treated some running rigging with various products and will report back with our findings.

PMI Rope Washer


We washed yards and yards of rope to find practical answers in the form of procedures rather than product selections. These are our bottom line lessons:

Never wash a new rope. Specifically, we learned that new double-braid dock line that is washed in a machine herniates right through the shell, that splices come loose unless whipped and stitched, and that every line is vulnerable to overly vigorous washing. Give them a light scrubbing with a brush if you must, and leave it at that.

If you must wash a rope in a machine, think twice; are you willing to ruin the rope? If so, then take sensible and proven precautions: whip and stitch all the splices or they’ll come loose, whip or thoroughly melt and fuse all rope ends, cover shackles with old socks to protect the machine and the shackle, always coil tightly or daisy chain the rope, and package the rope in a pillowcase. Skip the pillowcase and expect both rope and machine damage; we experienced both. And certainly, use the gentle cycle. If the gentle cycle doesn’t do, soak first and then scrub a bit by hand.

As for soaps, cleaners, and chemicals, we learned ordinary laundry detergents at ordinary doses are fine for older ropes (remember—you shouldn’t be washing young ropes) and an extended soak in a mild detergent really helps soften stains without risking damage. Bleach didn’t do much that the sun won’t do and poses much greater risk. Acid is deadly to ropes; don’t even consider it.

When we followed these simple rules, the ropes were undamaged and results often surprisingly good.

Comments (1)

An informative article. I am wondering if consideration was given to use of diluted Saltaway or Salt-X products to assure complete removal of sea salt crystals? Would there be an advantage here or is a soak in warm water sufficient to remove all caked-on salt? I'm thinking an initial gentle soak could stop further abrasive damage by salt during cleaning. Jim Gordon KOAN 4

Posted by: Jim G, S/V Koan 4 | July 30, 2011 11:09 PM    Report this comment

New to Practical Sailor?
Register for Free!

Already Registered?
Log In