Updated: I've posted a video of my plaque cleaning technique HERE!
Oboe reeds are made from organic material, and over time it is inevitable that they will age and change.
The first few days of change are usually quite welcome, as you break the reed in by playing and the opening gradually settles down to something you can be comfortable with and the response becomes more and more predictable. You might even hit a plateau where it appears to be perfectly consistent and reliable for several days! But after that, the reed seems to be on a constant gradually accelerating downslope, until it eventually collapses into a sharp, non-responsive, mushy mess.
We can rejuvenate the reed during this time by cleaning it, and can often extend its life as well!
There are three good ways to do this.
First, least invasively, you can just run some fresh water through and over the reed AFTER you play each time. Go ahead and rinse that reed in the sink, shake it as dry as possible, and tuck it right back in your (normal, well-ventilated) case. This removes most of your saliva, with all of its proteins and enzymes which are designed to break down organic material, and lets the cane rest as inertly as possible.
This always seems like a great idea and I never actually get to it. At the end of my practice session or rehearsal I am always in a hurry to move on. So my other two solutions are ones that can happen right in the moment, as you feel the need.
Alternately, you can use a thin pipe cleaner or a very small feather and send it through very gently from the cork end out through the tip of your (well-soaked) reed. This removes the gunk that accumulates within the reed over time and refreshes it quite a lot.
(Sidenote: This gunk is, I think, very much like the plaque that builds up on your teeth between brushings. It's natural and not inherently dirty, but getting rid of it makes everything smoother and more vibrant.)
I'd suggest using a different pipe cleaner each time, because ick.
This is also an effective choice that I rarely do myself, due to the inconvenience of digging clean pipe cleaners out of wherever I stashed them the last time I needed one. Most of the time, I just use the tools that I have at hand.
My favorite solution is this: you can scrape that same gunk layer off the inside faces of your well-soaked reed with the edge of your reed-making plaque, especially (but not exclusively) if you have a plaque with rounded rather than pointy ends.
You can clean the same (usually thinner but not nonexistent) gunk layer off the outside of the reed with your sharp knife and NO PRESSURE at all, or with the
long side of the oval of your plaque. You're not trying to rebalance or remove cane here, just to polish the surface of the reed and take off any old dead material.
This is what I most often do for my students when they come in complaining about their reeds. I hear a complaint like "this reed seems stuffy and small", or "the reed seems to always feel dry even when it is soaked up", or "my band director says I'm REALLY SHARP" and my first instinct is to use my plaque to scrape the inner surface of the reed. It's frequently the only fix we need.
Give this a try! Let me know how it works out for you! Can you get more vibrancy or more longevity from your reeds? I think you can!