[Brewer Gerard]

Perhaps it's not completely clear from how I've described it but what i meant was there is no change from purple back to clear. As i said, the hop solution is 0.1 lower in pH than the water it's boiled in.

[Brewer Gerard]

I'll do the experiment again with triple concentration of hops returned to only 5ml of reagent. If the solution doesn't clear i call horse crap on home hop alpha acid testing

[Borek]

As described the procedure makes sense, it doesn't differ from what I would try.

But I don't get what you wrote, sorry.

You boil the hop.

You wait till it cools down.

You add phenolphthalein to the brew. What color is the solution?

[Brewer Gerard]

Sorry about the lack of clarity.

I make 100ml of hop solution.

I make 10ml of 1 % NaOH solution and add a drop or two of phenolpthaleine (now purple).

I return the hop solution in 5ml steps to the caustic solution in the belief that the acidity of the hops will clear the sample.

It doesn't work

[Arkcon]

I wouldn't have expected it to.  A 1% solution of sodium hydroxide is 0.25 M.  You can vacate the color of a trace of phenolphthalein with a similar volume and concentration of strong acid.  The weak acids we call hops alpha acids are not strong enough.

Now, if you could make a 0.1 M (that's 4 g NaOH per liter,) or 0.01 NaOH solution (dilute previous 1:10), and you color it faintly magenta with one drop of a phenolphthalein TS (that's 1 g phenolpthalein per 100 ml alcohol), then maybe you can determine total weak acid in your hops sample.  Again, review my comment, this is just a ballpark alpha acids content.