After working on more conventional paintings I returned back to the canvas staining experiments to see if I could hone the technique to achieve the effects that I wanted to. It appears that I can get a nice clean edge to the rectangles using the frog tape but it is not 100% reliable. For some reason it is much harder to get a crisp edge with the blue paint. I can not work out why as the mix is mostly made up of water the same as the others but for some reason it seems to bleed under the masking tape.
I have also discovered that it is almost impossible to get a nice clean edge with masking tape when it is used on a previously painted area of canvas. I just cant work out why this is as I am leaving a day or two for the paint to dry before using the tape.
A look at the picture below shows the differences in the edges. As can be seen there is some really sharp edges and there is some where the paint has either lifted the masking tape or soaked through the canvas. This is not good enough for what I want to do so I either need to find a reliable solution or an alternative method of producing the work I want to.