One of the great 78 rpm collectors in the United States is without a doubt R. Peter Munves who worked for RCA. I had a short but meaningful relationship with Mr. Munves during which he told me cactus needles SHED FIBRES INTO SHELLAC GROOVES AND BY FRICTION ARE WELDED/BURNED IN. He says this accounts for the scratchy sounds of English HMV; that everyone in England used cactus needles, that's why they are so noisy. Now, to his credit, I must say, I have many HMV records that were imported from the UK for radio performance only and they are less noisy than ones brought into the USA taxed and many second hand brought over in suitcases but from what information I have attempted to gain on the subject I cannot find one bit of information to substantiate R. Peter Munves' claim.