• HowLett Impact Lab

We tried to make mailers out of stone.

Have you heard about stone paper? It is a cool new material that is made of 80% calcium carbonate (waste material from limestone quarries) and 20% HDPE (to bind the stone powder).


At the HowLett Impact Lab, we are committed to keeping our packaging out of landfills.


We envision a world where brands only use low impact packaging. Right now, we are working to introduce new materials, techniques, and sustainably focused designs to brands, allowing them to reduce their environmental impact.


Needless to say, we were really really excited about stone paper. We thought it could be a

great alternative to polymailers. You see, stone paper is advertised as waterproof, crease resistent, extremely durable, and not able to tear or puncture.


I’m sure stone paper really is all of the things describe above when you compare it to computer paper. Most sellers compare stone paper to tree paper…for good reason. But we tried to use it to replace the big bad polymailer.


Polymailers are extremely attractive for packaging, they are lightweight, durable, waterproof, and easy to print on. But they are also very polluting. Polymailers are typically made from 100% virgin plastic. Polymailers (and all flexible plastic film) cannot be recycled in most curbside recycling program because the material clogs the plastic shredders in recycling plants.


Now, you might be thinking, but stone paper also has plastic in it. Why would we want to use it? Yes, stone paper does have a small amount of #2 plastic, HDPE. But this is still an 80% reduction in plastic from the original 100%. That’s a big reduction!


Stone paper is a tree-free product.


It requires very little water, acid, or bleach in its production. This means that it will not pollute the air, rivers, and drinking water with harmful chemicals. Stone paper requires significantly less energy and has lower carbon emissions than both virgin and recycled pulp paper. Any trimmings or wastepaper from production can recycled to make new paper.


Due to the HDPE content of stone paper, it can be recycled with the conventional #2 plastic recycling stream. Does stone paper have the same problems and poly film mailers in recycling? No! Stone paper is not stretchy, so it will not get stuck in the plastic shredders. It is thin and flexible, while still being rigid (think single use water bottle) so able to be recycled. Stone paper can also be burnt for energy without creating toxic gases or leaving behind any harmful residue.


Our stone mailer prototypes had punctures and tears when we tested it in the mail.


In the end, our intentions were good but stone paper did not hold up in our shipping tests. Don't worry, we're still trying out other innovative new materials. Although stone paper is advertised as being strong and resistant to punctures, we found that it did not keep integrity in transit when shipped from one of our office to the other.



While envelope mailers might not be the best application for stone paper, we continue to look for new uses for this more sustainable material. In the meantime, ask us about our compostable mailers! We came up with a water resistant and durable mailer that bypasses the recycling system completely because it is compostable. Look out for more information about industrial composting and what that means exactly.