If you talking about Minwax wood hardener, the problem with it is that it IS NOT waterproof! If wood that has been treated with it gets wet, it will produce a "milky" colored hazed throughout the wood.
I found this out by accident several years ago, I was playing around with stabilizing, and had tried Miniwax wood hardener on a batch. I had set it out on the picnic table to dry, and forgot it overnight....we had a heavy dew that might, and the next morning when I found it, all the pieces where pasty white on the outside, and when I cut into them, where milky all the way through!
Although some folks have reasonably good ways to stabilize, after that incident, I gave up on it. For me it's not worth the wasted time and materials when I can just have it done by the professionals, and be confident that I'm getting the best finished product I can.