This is my biggest problem area in reed making. How do you deal with this part? This is where I usually ruin the reed.
Do you cut the scrape with knife and sanding; no sanding; or do you use a chisel or gouge to start it off like Cillian O,Briain does … ?
What do you use as a guide to the shape of the scrape?
Do you wet the reed along the way?
Thanks in advance.
sharp chisel,the cillian way is what i do,quick and easy.he does it in shot,but i take a little at first in the center to get started,then abit more,finish with sanding.do not sand to much in the center near lips,will cause sinking back d. 
Douglas,
I am totally with you on the scrape part of reedmaking being the hardest to master. I used to get (and still sometimes get) really flat back Ds and gurgling bottom Ds out of my reeds, but have found a scraping proces that works well for me now.
My previous focus to get a reed playable was to focus on the base of the scrape as this rapidly improves playability and eliminates bottom D gurgles, but has the drawback of flattening back D just as rapidly. I only recently found success when I moved my focus to the upper portion of the scrape to improve the playability and eliminate the gurgles with the added advantage of the back D not getting so rapidly affected.
My method to create the scrape is to go with sandpaper for the majority of the process and just finish the sides of the scrape and bring symmetry to to it using a stanley knife. Although the sanding from the start takes longer than creating a basis of a scrape by slicing off a chunk of cane, I like that there is less room for error using paper and maintaining symmetry is easier as you cant take too much cane off too quickly. I just wrap some dental floss above the binding over a few millimeters to prevent me from sanding a scrape area that is too long and start off with very coarse paper (100 grit) to give me a head start.
My sanding process is as follows (should you wish to try it):
With the reed blank horizontal, I sand back and forth until I have a 20mm rectangle of about 5mm in width (finger pressure more towards the base of the reed).
I then angle the the lips of the reed down and transfer the finger pressure towards the lips to turn it into a ‘V’ shape that curves out at a steeper angle at the top (stop when there’s about 1mm of bark left in the corners.
I then start to angle the reed sideways (a few strokes on the left then the same number of strokes on the right) to get straight sides to the ‘V’ shape.
I then remove the floss and scrape with the knife to extend the scrape by 4mm into more of a point than the current squared bottom and put some arc into the straight sides of the ‘V’ shape.
Finally, I use some finer sandpaper (240 grit) to just thin the lips and I focus mainly on the corners so that the lips are thicker at the centre than the corners (centre thickness of lips when closed = 0.6mm).
If you keep checking on the shape you are creating with the sandpaper, you can adjust your angles or pressure points to correct any mistakes that you are starting to make (e.g. When I think I’m creating the initial rectangle shape in the centre, I find that it is to the left of the centre point so after spotting this, I start intentionally leaning the reed sideways to counteract it before it the scrape gets too wide).
Assuming you’ve gotten to this part of my post without giving up on reading all my waffle, which was intended to give you adequate detail to recreate my method, I hope it may be useful for you and bring you some success.
Good luck.
Thanks for the responses.
Goldy, I will give that method a go. Your method kind of deals with the “second scrape” right from the start. Thanks again.
Doug