This seems like a somewhat awkward set up to me Tim. Is there some reason why you didn't just remove the hilt and immerse the blade totally in something like pineapple juice. I wouldn't think the citrus is all that helpful to the hilt anyway. With total immersion you wouldn't have to worry about moving the blade in and out all the time. The cleaning would be more even. I'm also not sure you will get a "white" blade this way. If your photos are any indication it looks like the citrus has re-activated some of the old warangan. At least it appears that the iron is darkening in some areas, especially around the edges and lightening where there may be pamor. But perhaps that is just a photographic illusion. If you plan on re-staining this one you might need to employ a bit of scrubbing to get this tombak "white". Of course, if you don't plan on restaining, the lemon treatment might just bring out the pamor to your satisfaction.
Either way, be sure to neutralize the citrus with something like a slurry of baking soda to stop the action of the etch.