Keep Earth Beautiful, Process Waste Water before Dumping

January 14, 2019

Acrylic waste water contains pigments that are harmful to the environment. Rinsing brushes in the sink deposits the pigments in our rivers, lakes and oceans. Dump your waste water in a bucket in your studio and every week or so process the paint solids out. I learned how to do this from the Golden website. The article is here. It sounds scientific and complicated but it's really not hard and it will make you feel good about doing your part to help protect the Earth. Please do this. Message me if you have any questions.

a five gallon bucket approximately half full of water that was used to clean paint brushes

Acrylic paint waste water. What do you do? Dump it down the drain? NO WAY!

materials for procssing water based paint paint solids from rinse water, buckets, line aluminum sulfate, coffee filter, funnel

Assemble the materials. Lime from garden supply, aluminum sulfate, large coffee filter, funnel from auto supply store, buckets, measuring spoon, ph paper

funnel to hold coffee filter sits in the lid of a five gallon bucket

Cut an opening in the lid that fits your funnel.

aluminum sulfate add to rinse water

Add about half a tablespoon of aluminum sulfate per gallon. I am processing 2.5 gallons so I'm using 1.25 T. Don't worry too much about exact measurements. Just do it.

stirring vigorously the rinse water to mix in the Aluminum sulfate

Stir vigorously!

add lime to rinse water

Add Lime, a scant .75 T per gallon. I mix up the Lime in a glass jar with a little water and shake it otherwise it tends to clump up in the bucket and not mix well.

waste water showing the paint starting to flocculate

Dump the Lime into the bucket and stir. You should be able to see the paint solids start to flocculate almost immediately. I love that word, flocculate, and if you do this you'll have more opportunity to use it.

pH paper showing a pH of approximately 8

Test the pH of the water. It has to be between 5 and 9. I aim for 6 or 7. If it's lower than 5 add lime. If it's higher add aluminum sulfate.

cleansed water being poured through the coffee filter

I let the solids settle to the bottom of the bucket and strain out the clear water first.

turbid water poured into the coffee filter set up

When I get to the bottom of the bucket the water is clouded with the paint solids. It takes longer now for the water to pass through the funnel so I fill it up with the rest of water and leave it for the night.

paint solids sit in the coffee filter

The next day the paint solids are well strained and already beginning to dry out.

coffee filter holding acrylic paint mud

Coffee filter with the paint solids can be thrown in the trash.

clear water in a bucket

Et voilà. Clear water that can be safely poured down the drain. I asked a chemist friend and she said it could even be dumped in the backyard or re-used in the studio.

hand holding pH test strip showing green. bucket of clear water behind.

Test the pH, just to make sure it's right before dumping down the drain.