Anyone ever add any plastic shreddings (PVC) to their homemade rock?  I heard this also helps in making it lightweight, as well as a good starting point for coraline to attach too. 
 
I have never made any rock myself (yet)  So if someone around calgary is going to make any soon, I would like to tag along and watch/help 
 
 
Jim 
		
	
		
		
		
		
		
	
		
		
	
	
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