I am no etex expert. But I read a post on here about a year ago, that said the hardener would yellow after it sat for a long time. I had my old bottle for a year and didn't notice how yellow it really was until I went out and bought a new bottle. The new etex hardener, is only slighty darker than the resin. Also, I went to walmart and bought 2 clear ketchup or mustard bottles with caps. They are super easy to dispense the proper amount of the hardner and the resin. I found trying to pour the exact amount sout of the original bottles to be difficult and really messy! Plus they only cost .97 cents.