Chemistry and Coatings - Avoiding Spring Wash

Most of us know what would happen if we sat on a freshly painted park bench or leaned on a freshly painted wall. Coatings, like paints - and also like mulch colorants - need time to dry to “lock onto” the surfaces they are coating. The coatings will adhere to any surface that makes contact with them when they are wet – including the surfaces of droplets of rainwater! Once dry, even if water is later poured on them, the chemical bonds that secure them to a surface remain intact unless chemically broken or physically rubbed off.

While mulch colorants are different than paints in many important ways, one way that they are the same is they both require drying time to lock onto the surfaces they are coating. However, many mulch producers expect a pile of mulch will react differently and will stay on the wood before drying. Every year we hear from at least one newer mulch producer who ran product wet or exposed it to rain, and then reported the colorant was not good because it ran off in the rain.

Three things are important for allowing your mulch pile to dry thoroughly – time, humidity and airflow. Obviously, there’s a certain amount of time required for proper drying, but humidity and airflow play a big part. If it’s very humid, things take longer to dry. If it’s raining, they may not get a chance to lock onto the wood surfaces at all. It is recommended that mulch producers check their weather conditions, and not color during rains, and to also allow extra time for piles to dry if the weather is humid. The other key is for the producers to rotate their mulch piles. They need to get into the middle of the pile, to get the fiber out to the air to allow it to dry. Conditions inside a big mulch pile are not conducive to drying – too dark and damp.

In the event product “washing” does occur, there are a couple of options available to replenish the material. If the material is in a bulk pile, the product can simply be rolled back into the pile. There will be enough colorant and moisture in the pile to coat the surface material.

If the material has been applied to the landscape, there are three options to remedy the situation.

• Lightly rake the surface – colorant loss is normally limited to the top half inch of material. Mulch is normally applied at a two-inch depth leaving plenty of material to cover the surface.
• Top surface with an additional half inch of fresh color-enriched product.
• Again apply colorant to the surface with water and colorant solution. A mix ratio of 20:1 will provide excellent results.

It is also important not to allow the run off from a wet pile to flow into storm sewers or local creeks, where it can flow into the watershed. While the colorants Amerimulch uses are safe and, when diluted, pose no hazard to the environment, the sight of red or black waters still causes concern among local fire departments and water treatment officials.

To recap, producers can limit the opportunities for product washing to occur during the spring season by following the options noted below:

• Limit all deliveries when rain is forecasted within the next 24 hours.
• Call all customers receiving material and express the concerns of spreading the color-enriched mulch on forecasted rain days.
• Produce and inventory the products two to three weeks prior to shipment.
• Inventory products in windrows, not bulk piles to maximize surface area or drying area.

The more effort that is proactively placed on preventing spring wash from taking place the less effort is required once it does. On the bright side, spring wash means winter is over and we can spend more time enjoying the outdoors.