Oh No! I have a stain on my wood pallet.

There is a stain on my wood pallet, now what?

Don’t panic. Stains on pallets are usually not a concern. Find out why and how stains happen.

Stain where nails are in contact with an oak deckboard after the HT process. Note that stain runs down the non-oak stringer.

Pallets made of yellow poplar with the same nails and the same HT process. No stain.

Let's take a closer look at wood. Wood is made up of: 

• cellulose
• hemicellulose
• lignin
• minerals 
• water soluble extractives
  

With the exception of the water soluble extractives, these components are relatively stable when using wood for pallets.

Except for oak, most wood species used in pallets have a low level of extractives. Oak is one of the strongest and most durable of the pallet materials. Unfortunately, oak also has some of the highest levels of these water soluble extractives.

When oak comes into contact with metals like steel - and moisture is present - these extractives can react to create blue or black stains. Staining does not cause performance loss but it can be an issue with products sensitive to discoloration.

Any of these metal contacts will create the stains:

• All wood pallets have nails.
• Some are secured with steel banding. 
• Some products are even uncoated steel.
  

For international shipments staining can become even worse. Required heat treating brings large amounts of moisture to the surface of the pallet.

This pallet has an oak board in the front and maple board in the rear. There is stain on the oak board but none on the maple.

This stack was secured with steel banding. The banding stained the oak stinger, but the other non-oak stringers are not stained.

Stains are OK for most products. If you find the stains to be a problem, try these solutions:

• Request dried pallets or used pallets. Without moisture, the staining process is less likely to occur - even with oak.
• Use a slip sheet or other moisture barrier to protect your products from the stain.
• Request hardwood pallets without oak. Since many pallet customers want oak, it may be possible to have your pallet supplier segregate out the oak and give you other hardwood species less likely to stain.
• Request plywood or other panel pallets.
• Request softwood pallets - they don’t have the same staining potential.
• Request plastic or other non-wood pallets.

Do you have a stain on your wood pallet that concerns you? Snap a photo and post it below. I will evaluate your stain and give you feedback on what you can do to avoid stains on your wood pallets.

Post by: John Clarke, Technical Director