The method of priming drops I am outlining is not the method used by professional scenic artist. I have found that, for the novice or intermediate theatre technician, that this method works well to both size (shrink) and seal the material to prepare it for painting your design. I like this method because it is quick, easy and keeps the drop from getting very heavy. When I began painting drops, I used a roller with the drop taped down (or stapled down) onto visqueen. (Black plastic from the hardware store) It was difficult. The material would roll up onto the roller and I would go through large amounts of paint. This made it so I could only use a drop once or twice. When rolled up at the end of a show, the paint would crack and peal because of the thickness. I wanted a way to eliminate these issues. The steps listed below outline what I came up with and have had success using. (This method works great with soft flats as well.)
1) Lay your drop out on an open space. It is preferable to paint the whole drop at one time as it will reduce irregularities in the drop. You can paint one part of the drop at a time as long as you let it dry completely before rolling it up on itself to expose the next section. When I have done this, it is not uncommon for there to be wrinkles or puckering along the seam between the two areas as they will dry differently.
2) Lay down the drop onto Visqueen. Tape the edges down with Gaff tape so it is less likely to move.
3) Use a good primer with a low quantity of filler such as Rosco’s Tough Prime. Mix one gallon of primer with one quart of binder/acrylic such as Rosco’s Clear Acrylic or Sculptural Art’s Plastic Varnish. The clear acrylic will allow you to thin the paint very far without the paint becoming chalky and flaking off the surface. (Using the binder/extender also allows you to make excellent glazes as well) (You can add Rosco Flamex Paint Additive to the gallon if you would like to have the drop fire resistant when finished)
4) Dilute the mixture with water until it is the consistency of milk.
5) Pour the diluted mixture through a strainer into a hand sprayer (Often called a Hudson sprayer.)
6) Pump up the sprayer and spray the thinned mixture onto the drop. Have one or two people go behind with a 6 or 7” lay-in brush using a cross hatch motion. (A series of big “X”s on the canvas) Work the paint into the weave of the fabric. Make sure the fabric is completely soaked through with the mixture.
7) Go over the entire drop using this method.
8) Allow the drop to dry. The process of drying will shrink your drop by about 10%. (Assuming this is untreated muslin)
9) This will create a light primed drop that is ready to paint.