What is the longest word you can make by adding 1 letter each time to a single word?

Question

Example: A
An
And
Band

The words must be real words, and you can add letters between, before and after other letters.
What's the longest word you can make that follows this pattern?

Answer 1

This is my best so far (last word = 9 letters):
I
IN
SIN
SING
SINGE
SINGER
SINGERS
STINGERS
STRINGERS