patterned canvas in Portugese masterworks and a tablecloth...

Recently I have found a publication by Rita Maltieira in which is shown that Portuguese Old Master painters also used a patterned canvas for their work. Until now I have only seen this patterned canvas in paintings from Spanish and Italian Old Masters.

I could not believe it when Jan Bustin, conservator in the Netherland, send me pictures of a tablecloth that he owns with , at first sight,  a very similar pattern. 

I will soon receive better quality pictures from the canvas and analyse both textiles to make sure it is the same pattern.

Both this two findings are very important, its may give another 'piece of the puzzle' in the story of painters canvas.

The canvas, hidden in plain sight, as in one of the comments, and for centuries and now with the topic question :'Why did they use this patterned canvas' ?
Stay tuned!
canvas as used by Portugese painters 

a tablecloth, owned by Jan Bustin