Dahlias in a Silver Lustre Jug - drawing the subject

Today I'm going to explain how I make the initial drawing for the painting onto my panel, using comparative measurements. 
Here's a photo of the subject.

To make the measurements, I hold out a paintbrush, keeping my arm straight at the elbow. I mark the measurements with my thumb  on the paintbrush. 

First I measure the height of the arrangement, and then keeping my thumb in the same place on the paint brush, and my arm still held straight, I rotate the brush by 90 degrees to compare the measurement to the width of the arrangement.  

I find the height of the arrangement is slightly greater than the width, so I mark a rectangle with these proportions by eye on my panel. I'm using a mixture of burnt umber and ultramarine blue thinned with medium to make the drawing. If I make any mistakes, I can easily wipe them away with some white spirit.

Next I make some comparisons of the main proportions within the still life arrangement. 

The first comparison I make, of the width of the flowers to the height from the bottom of the jug, shows the width is approximately 3/4 of the height 

Next, I note that the width across the bottom flower to the right hand edge of the jug, is approximately the same as the width of the top flowers.

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I find the height of the jug, and compare it to its width. I find it's about twice as tall as it is wide.

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I plot the points I have measured within the initial rectangle I marked out.I draw another rectangle divided vertically in half to help draw the jug.  I find marking the halfway point helps me to keep the jug or vase symmetrical. 

I check the angles of the sides of the jug with my paint brush.  

Here I'm working out the relationship of the handle to the rest of the jug.

Now I have enough information to plot all the outermost points of the arrangement, at this point you can carry on using comparative measurements to complete your drawing, but I usually fill in the rest by eye.

Heres the finished drawing.  The proportions aren't 100% accurate, but they are close enough to make the painting work.

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If you have any questions or suggestions, please leave them in the comments below.