Sprinkle Corte*Clean® powder directly onto the stubborn composite stain(s) when the composite is wet with Corte*Clean®, in direct sunlight above 65 Degrees Fahrenheit. Make the Corte*Clean® powder into a paste, scrub the affected area with a brush that will not damage the composite, let the Corte*Clean® work for up to 20 +/-  minutes or until the Corte*Clean® becomes dirty or discolored, then hose off. KEEP THE COMPOSITE WET WITH Corte*Clean®, DO NOT ALLOW DIRTY CORTE*CLEAN TO DRY ON COMPOSITE! Rinse with water. Water magnifies stains. Allow composite to thoroughly dry. Repeat the Corte*Clean® application process until thoroughly clean.


Before composites receive moisture and stains appear or when stains first appear. Spring, summer, and fall or whenever the weather permits. We have found it best to start Corte*Cleaning® in the morning (AM hours) when the temperature is at least 65 Degrees Fahrenheit and the temperature is rising in DIRECT SUNLIGHT and the composite has been thoroughly dry for several days to weeks. When the temperature gets above 85 Degrees Fahrenheit, Corte*Clean® works great but evaporates too quickly, resulting in the need to continually apply Corte*Clean®, wasting product (your hard earned money).

Yes, Corte*Clean® has been proven effective for removing citronella stains although it may take several repeat applications at maximum strength. Be sure not to allow the citronella to solidify! It is best to use warm water and clean on a hot day. Mix Corte*Clean® with warm water around 100 degrees F.

NO, especially if it is a man made and/or recirculates water.

Heavily water plants and grass before and after using Corte*Clean® to “protect”. Cover plants and grass with plastic for additional protection. Do not spray Corte*Clean® directly on to plants or grass. If over spray of Corte*Clean® comes into contact with plants or grass, immediately rinse with water. Keep sprinklers on if possible. NOTE: In small, diluted doses, Corte*Clean® should not kill plants or grass.

If mold stains are the primary issue, it is a good idea to proactively routinely Corte*Clean® the composites, at least twice (2x) yearly, Spring & Fall, before they receive moisture and stains appear or saturate into the composites. Composites located in areas known for mold spores and routine moisture should be cleaned more frequently. EXAMPLE: Spring, Summer, Fall, Winter.

Corte LLC has found it necessary to Corte*Clean® a composite at least twice (2x) per year or whenever the owner considers a composite to be dirty. Spring and fall are generally best do to the climate. Others have found it necessary to clean a composite, more or less often. This is generally do to the climate in which the composite is located, what it is exposed to, how it is used and how much moisture it receives. If something is spilled, dropped, or one notices new spots or stains, clean it ASAP! The longer the owner procrastinates cleaning a composite, the more it costs (time & money) to get it clean. For Mold Stains (black spots); see other FAQ.

Corte*Clean® should only be used to “SPOT” clean once a composite has been thoroughly Corte-Cleaned. If it is used to “SPOT” clean prior to thoroughly Corte*Cleaning, it will only clean where it is applied. This will likely result in ugly clean “SPOTS” on the composites.

Unfortunately, most exterior building materials, including composites, glass, concrete, brick, roofing, etc. require regular cleaning to preserve the appearance, especially after it rains. Composites are no exception. Thankfully, composite owners won’t have the additional cost or labor of painting, staining or sealing in order to preserve your expensive investment. Neglect and decay of treated wood, redwood, cedar or other organic materials is the #1 reason most wood decks, docks & fences are replaced with composites.

Wait and let the sun naturally weather them out. These spots are likely from stains blocking the sun from evenly weathering the composite. Stains can act as an umbrella. Stains block the sun from evenly naturally weathering the composite. It generally takes the same amount of time for the composite to evenly weather by exposure to the sun as the composite was neglected to be cleaned.


  1. They don’t purchase enough Corte*Clean® to thoroughly clean  composites, especially if they have never used it, have tough deeps stains from mold, grease, oil, rust, etc. or have previously attempted to clean mold using chlorine bleach or other sodium hypochlorite containing biocides.
  2. They do not allow the composite to thoroughly dry before cleaning fungus stains or re-peating the application process.
  3. They don’t read & follow the Corte*Clean® label directions and use Corte*Clean® at MAXIMUM strength in direct sunlight and allow composites to thoroughly dry before cleaning “black spots (mold stains) or other difficult to remove stains.”
  4.  They use do not “repeat the application process until the desired level of cleanliness is reached” and thoroughly Corte*Clean® the stains.
  5. They don’t allow enough time to thoroughly clean a composite.
  6. They cut corners while cleaning the composites.
  7. They don’t Corte*Clean® the composite when they begin to notice stains, but instead choose to procrastinate until  it becomes more difficult to clean, costing more money and time.

Corte LLC is trying to be as environmentally responsible as possible with Corte*Clean®. Shipping water weight is incredibly environmentally irresponsible, especially if it can be avoided. It  unnecessarily uses fossil fuels that pollute, cost additional money to ship and is heavy for our customers to carry. One must have a water source where the composite is located. Therefore, Corte LLC has chosen to ship Corte*Clean® in a powder form.


YES!!!Prior use of sodium hypochlorite in an attempt to clean mold stains from a composite may make it more difficult, expensive and require additional time.  Additional “repeat” applications of Corte*Clean® at “MAXIMUM STRENGTH” will likely be necessary to get the composite thoroughly clean. One will likely need additional Corte*Clean® to get mold stains out of composites if sodium hypochlorite has been previously used.


NOTE: The first time sodium hypochlorite based products are used in an attempt to clean mold stains from porous composites, they generally appear to quickly bleach out the stains. With repeated use, they generally have little if any effect in cleaning  these stains. You will find this to be true when the composite no longer SPOTS but turn solid black in color.

If you have used sodium hypochlorite in an attempt to clean mold stains and could still see where they were when the composite is/was wet, the stains generally immediately darken and return when the composite receives moisture from rain, humidity, morning dew, snow, etc. Perhaps if you have previously used sodium hypochlorite based products and noticed this. Here is a photo of what this looks like and Corte*Clean® resolving the issue on ChoiceDek®…

Just like children, bare skin, wildlife, don’t let any animal eat, drink, walk on or come into contact with Corte*Clean®. It is a powerful cleaner!

Yes. It is best practice to use warm water and clean these stains on a warm day. You don’t want these items to solidify.

It depends on how dirty and stained it has become. The longer a composite owner neglects to clean a composite, generally, the longer it takes to Corte*Cleans® a composite. This is because it generally takes additional repeat applications of  Corte*Clean® at maximum strength to a thoroughly dry composite. This is why Corte LLC recommends cleaning a composite at least twice per year. The average size deck is 300 Sq. Ft. and generally takes a couple of hours to half a day to clean. The bigger, dirtier and more stained the composite is, the longer it takes, especially if the Corte*Clean® application process is needed to be repeated numerous times, to a thoroughly dry composite surfaces, to remove deep stains. The more often one Corte*Cleans® a composite, the faster and easier it becomes. To proactively Corte*Cleans® a 500 Sq. Ft. composite deck, before it receives moisture and stains appear or deeply saturate, can take as little as an hour. The longer one procrastinates to Corte*Clean® a composite, the longer it takes to get it clean, especially when it comes to mold stains that have been allowed to root deeply into the composite, mold that has not been allowed to thoroughly dry out or grease, oil, rust, etc. has been allowed to deeply saturate.

Yes. Corte*Clean® is designed to stick to the surface of composites and fill into the composites pours. This allows Corte*Clean® to re-activate any time it receives moisture until it is thoroughly rinsed. The less thoroughly the composite is rinsed of Corte*Clean®, the longer it will continue to clean any time it receives moisture until it is thoroughly rinsed. Always thoroughly rinse composites before letting anything living on it such as bare feet, small children, pets, animals, etc.

Corte*Clean® is a chemical! Like most chemicals, it should always be stored “Store in a Dry, Cool Area Out Of Direct Sunlight.” A Dry, Cool, Area is not in the high 80’s, 90’s or over 100 degrees F. A “DRY” area means low to no humidity and no moisture. “COOL” means cool to the touch, not warm or hot. 78 degrees F. and below is a perfect storage temperature for Corte*Clean® although cooler is better but above freezing. If you do not properly store Corte*Clean®, it could loose strength and not properly remove stains making the product worthless.

Aspergillus Niger mold is believed to be the most common species that stains composites. The second most common species is believed to be Stachybotrys.

Corte*Clean® is safe to use on plastic vinyl railing, fencing, etc. If you choose to use Corte*Clean® vinyl railing, always test Corte*Clean® on a sample piece or small inconspicuous area or sample piece to make sure you are satisfied with its results. If you are not, do not use it for this purpose or on this surface. Generally a good car washing soap that is designed to come into contact with plastic is all that is necessary to clean vinyl railing.

Corte LLC set out to solve the cleaning issues of composite decks, docks & fences. This is exactly what Corte*Clean® does. Should you choose to use it on other items, you do so at your own risk. Always test Corte*Clean® on a sample piece or small, inconspicuous area to see if you are satisfied with the results. If you are not, do not use Corte*Clean® to clean the item. Protect it with painters plastic.

Always, immediately, rinse these or any other items with water and wipe them clean with a rag before they dry. We have always “protected” these items with plastic if there was any chance Corte*Clean® could come into contact with them, therefor, we have never had this problem.

If you do get Corte*Clean® on glass, you will likely need a razor blade and glass cleaner to remove it. If you do get Corte*Clean® on aluminum, you will likely need a cleaner intended for this purpose to remove it.



Yes, however Corte*Cleans® can speed up the inevitable bleaching/fading/weathering or natural weathering, disclosed by most composite manufacturers, on the Corte*Cleans® label directions, and on the Guarantee & Limited Warranty on the bottom of every Corte*Cleans® bag.


Corte*Clean® breaks down into oxygen, hydrogen peroxide and soda ash. Corte*Clean® is considered a soap or detergent. If we made it any more environmentally responsible, it would not have the strength to remove tough stains. Although no man made product is 100% percent eco-friendly, Corte*Clean® is a far better alternative to our environment than the use of multiple cleaning chemicals such as those that contain sodium hypochlorite, such as chlorine bleach, and other deck washes that contain oxalic acid, phosphoric acid (phosphates),  TSP, ammonium, ammonia, etc. This is why we call Corte*Cleans® “ECO Responsible.” Additionally, Corte*Cleans® is a powder, so water weight is not being shipped, saving fuel and our environment.


Corte*Clean® breaks down into oxygen, hydrogen peroxide and soda ash. Corte*Clean® is considered a soap or detergent. If we made it any more environmentally responsible, it would not have the strength to remove tough stains. Although no man made product is 100% percent eco-friendly, Corte*Clean® is a far better alternative to our environment than the use of multiple cleaning chemicals such as those that contain sodium hypochlorite, such as chlorine bleach, and other deck washes that contain oxalic acid, phosphoric acid (phosphates),  TSP, ammonium, ammonia, etc. This is why we call Corte*Cleans® “ECO Responsible.” Additionally, Corte*Cleans® is a powder, so water weight is not being shipped, saving fuel and our environment.


Mold stains “SPOTS” will return to a thoroughly Corte Cleaned (can’t see mold stains when the composite is wet or dry), when the Corte*Clean has been thoroughly rinsed from the composite and new mold spores (seeds) land on the composite surface and receive moisture (rain, humidity, fog, snow, etc.)


If Corte*Clean® is beyond its “Best If Used By:” date, on the back of every bag, it will likely not work in cleaning composites, especially when removing black mold stains or other difficult stains because it looses strength. This is why the Corte*Clean® Guarantee & Limited Warranty, on the bottom of every Corte*Clean® bag specifically does not cover product that fails beyond this date.


Corte*Clean® is beyond its “Best If Used By:” date on the lower right hand back of every bag. The 2nd reason is that Corte*Clean® is not stored properly in a “dry, cool area out of direct sunlight.” Corte*Clean® stores best indoors; in a climate controlled area around 78 degrease F. but above freezing.


Yes, Corte*Clean® can be used to clean newer “CAPPED” composites, however, generally, at a greatly reduced strength. We suggest starting with 1 SCOOP of Corte*Clean® powder per gallon of water. You can alwayse increase the strength, if needed, to remove stains.

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  1. I run a handyman business and one of the many tasks we do is to clean decks. There is no other product or method of cleaning that I have found to be as effective as Corte Clean, nothing at all. Corte Clean is by far the best product for cleaning composite decking, it is so effective that I am now experimenting with using it on other surfaces.
    If you haven’t used Corte Clean yet, you will be amazed that it cleans so well, while using so much less effort.

  2. Is Corte Clean safe to use on a composite deck which has a rubber membrane under it?

  3. Generally, YES. However, it is always best to check with the manufacturer to make sure Corte Clean is compatible with the rubber membrane, as several rubber membrane manufacturers have tested and approved Corte Clean for cleaning composite decks with the products they manufacture underneath. With this being said, it is always best to test Corte Clean on an inconspicuous area or preferably a sample of any item you intend to get Corte Clean on, if not satisfied with the results, don’t get it on the item. It is always a good idea to attach a fan out sprinkler head to a garden hose and allow water to constantly dilute and rinse any Corte Clean dripping through the composites onto anything, including a rubber membrane, never allowing it to come into a dry surface, so it can’t clean the item, which could be perceived as damaging an item. This is an easy way to protect items under most composites.

  4. What kind of brush do you use for scrubbing the deck with Corte-Clean – stiff or soft bristle, nylon or natural fiber?

  5. The best brushes are generally synthetic, such as nylon, that is coarse enough to brush, but not so corse that they scratch or damage the composite boards. An example of a brush NOT to be used is a metal wire brush! Natural fiber brushes tend to blead tannins stains all over the composites that can be difficult to remove. Generally, one can’t brush deep stains from composites. Repeat applications of Corte Clean to thoroughly dry composites at maximum strength is what is necessary to remove deep stains from composites. Please call if you wish to discuss.

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