Start by spray painting the outside of the terracotta pots white. The spray paint doesn't have to look perfect as it will be covered with colourful paint. Allow the spray paint to dry. I usually find it will be dry to touch after about an hour.
You could also probably get away with skipping this step. I like my colours to be really vibrant (especially where there are thinner areas of coloured paint) so I prefer to paint the pots first.
Using tin foil or heavy cardboard, cut out a circle slightly smaller than the base of the pot. Tape the circle to the bottom of the plant pot. Make sure the tape is only on the bottom part of the pot and not on the sides. This is done to keep the paint from draining through the hole on the bottom of the pot. Also, it helps keep the paint from pooling in in the indented part of the pot on the bottom.
In the small plastic disposable cups pour about 1 cm deep worth of paint into each cup. I would recommend using quite a few different colours of paint to create a good marbled effect.
For our project, we used 6 different colours. This amount of paint covered 2 - 5" plant pots. If you are using larger pots or want to do more pots you will need more paint.
Add a very small amount of water to each paint (about 1/2 - 1 tsp). Mix together well. You want the paint and water mixture to be a consistency of a thinner syrup. If you add too much water just add more paint to the mix.
This is where I let my kids get involved. * When doing this activity children must be supervised.
For the next step below - because the paint we used was a craft acrylic paint and not a non-toxic kid brand paint, I actually just let my littlest guy (2 yr old) pick the colours and I poured them into the cup for him. My oldest (4 yr old) poured the paint into the cups with some help.
Randomly in no order start adding the paint to a new cup. You can re-add the same colour to the cup again. To cover a 5" plant pot, the cup should be 1/2 full of paint.
Place your plant pot firmly into the cup that's full of paint. Have a disposable box ready with a larger cup in it. The box is to catch the excess paint that runs off the plant pot. The larger cup is used to rest the plant pot on top of.
While firmly holding the cup onto the bottom of the plant pot flip the cup and pot over together. Place the plant pot over the larger cup.
Now it's finally time for the dirty pour!
Slowly remove the cup of paint off the bottom of the plant pot. Get ready for the paint to run all over and flow down the pot (see our video of this at the bottom of the post).
Put in a safe spot and allow the painted pot to dry (I would recommend for at least a day). Once dry, remove the tape and tinfoil circle from the bottom of the pot (be careful as this paint might still be wet if it has pooled).
Spray the plant pot with the clear protective Krylon clear coat. Once the Krylon clear coat is dry you're ready to use your new plant pot as a cute planter.
To preserve your new masterpiece I would recommend avoiding placing in a spot where the pot is exposed to elements like rain.