Keep in mind you ll want to fill your container up enough to be able to dip the vase inside without the plaster overflowing.
Make plaster of paris look like marble.
To make plaster of paris with glue instead of flour heat 1 cup 240 ml of water to 100 f 38 c.
To obtain a natural look for the veins get a dry sponge and gently tap the veins making the color blend with the ones underneath.
Acrylic polymer is white liquid it looks like milk it is mixed with water if you want at a rate of one to one.
The plaster should have a similar consistency to thick pancake batter.
Following the instructions on the plaster of paris container mix your plaster.
How to create a faux venetian plaster look.
Use a small paintbrush to add veins which should be thin and random.
Use this plaster within 15 minutes and let it set 3 days to completely dry.
Polished three dimensional faux venetian plaster enhances both the light and dark tones of the same color creating a sophisticated marble like effect.
And if you can buy plaster pigments that would be another good thing for you.
Or you can use it neat.
Use a sample of marble or a picture as reference.
The resulting plaster will have a soupy consistency.
Avoid following a pattern when painting the veins.
To create a marble like venetian plaster effect in your space you can use inexpensive paint and faux treatment tools for a fraction of the price of paying a professional plasterer.