I have around a kilo of lye and it's very hard to come by where I live. In the STB teks it says to use around 1gr. of lye for every gram of MHRB. Isn't that a over overkill? Do you really need so much?

I don't want to waste my lye. I need to use it for more things I'm experimenting with.

Has anyone used less lye and got less yield than expected?

well, the idea of the STB is to turn the solution really basic, so the plant cells collapse. If you don't want to waste too much lye, then you can try A/B extraction wich uses very little amount.
Where I live you can buy lye at every hardware store, like buying a candy, no one ever ask you nothing.
The other thing you can do is substitute lye with sodium carbonate. Take a look at the other posts.

My friend, do an A/B on that kilo.

You'll only need about a 1/4 cup of lye at the end if you use vinegar.

But yeah, I think that 1:1 is way overkil. If you can check your pH, just bring it up to 13.0 that is MORE than enough to break down plant cell walls and freebase damn near anything in the mimosa. You may need 1-2 cups for this depending on how much water you use (and don't use too little or you'll end up with the infamous mimosa sludge that eats naphtha and is a pain to work with).

best of luck, I hate STB's to be honest though. I've always gotten better results with A/B extractions...and there is so much less cleanup in the end.

What tek do you use?
Is 5% vinegar strong enough. I think I read that somewhere.

I use my own, it's a blend of Marsafold and some random teks I've found over the internet.

First acid cook (crockpots are great for this) 1:3 (vinegar:water) it doesn't have to be exact by any means. 5% is fine. Fill it all the way up. Stir frequently. Cook until steaming (~45 minutes is perfect). I don't usually let it boil, but hold it at steaming for 30-45minutes.

Strain

Put mimosa bark back into crockpot with 1:4 vinegar:water again it doesn't have to be exact in any way shape or form. Another 45 minutes at a steam, very light simmer.

Strain

Repeat with decreasing amounts of vinegar until the water comes out like pink instead of red, or the mimosa turns grey.
After my 3rd cook I don't add vinegar anymore, it's just not needed. Straight water from the tap

Combine into milk jugs, vinegar jugs, sunny D jugs, or whatever works.

Add lye, slowly, until the entire thing turns black with white streaks running through it. The more vinegar you use the more lye you will need. Shake for a min. Add naphtha 100-200mL for 500grams bark ~ again it doesn't have to be exact. stir around for a bit, maybe give it a little shake. Let settle for 10-15 minutes. Pull naphtha and stick into freezer. While that is freezing add another 100-200mL to your basified jug. Shake the hell out of it. When your freezer precipiation is done, switch naphtha (you'll need an extra 2 cups or mason jars for transfering the naphtha.

Repeat until jug is spent.

I can get anywhere from .8%-1.2% yield using the method and usually have very little clean up to do. Plus I'm only using a small amount of lye, saves me money and having to purchse lye online often.

Thanx for the info I have 1.5 liter of 15% vinegar so I'll use it diluted.

The main reason most STB teks suggest 1:1 is because this helps eliminate ANY POSSIBLE emulsion. You can use less, but when you have one huge bubbly mess, add more lye to fix it.

i use 1:1.
50g mhrb in
50g NaOH dissolved in
750 ml dH2O
with 50ml of naptha per pull.
it works great.

google food grade NaOH.
i think i pay $8 a kilo for it.
not only is it PURE FOOD GRADE, its cheap!!
the website i order from sells it for making candles or bio-diesel.

happy deeming!!

If you are using powdered bark you can use less lye but aim for a ph of 11.5-12. If you get lyelock(emullsion), add more lye.