How much does the quality of MHRB effect the yield?

I have just done an extraction using Cyb's hybrid salt tek and the bark I used was very dry with lots of hard chunks of bark. The first 2 pulls where clear until they hit the glass dish, then they turned milky, especially if blew on. The last 2 or 3 pulls where yellow/clear and didnt go milky when hitting the dish. THey have been in the freezer for 2 or 3 hours and the first dish is yielding, but less than expected. The second dish looks like a complete waste of time.

The only other variable is the size of the bottle I used which was larger than needed so I topped it up with an extra 400ml of deionised water to aid the pulling stage. Could this have also effected it??

Well the quality of the bark determines the maximum yield you can achieve. You can only extract what the bark contains, some bark is probably of a lower quality than others and will contain lower alkaloid content. Using a larger bottle on its own is not a problem, but adding the extra water will lower the pH, but I doubt it will have affected the yield too much. Buy a pH meter so you can always assure yourself you are at the correct pH, that way, if you end up with a poor yield, you can concentrate on what other variables may have caused the low yield.

2-3hrs is not where near enough time for freeze precip. I`ve had pulls that look to be almost zero until 10+hrs in. Other times not much more precipitated after 6hrs.

Wait a few days & see how it turns out. If the mhrb is top quality, I usually yeild 2% within 4 pulls. 3 is probably sufficient but I always just do 4 & slow evap down to a small amount before freeze precip.

If you havn`t, try evaporating down your seemingly empty pulls & freeze precipitating once they reach ~1/2 the original volume.

If all else fails, your bark is probably exhausted & that's all you`'ll get from it.