Quote Originally Posted by Gerald C Koch View Post
When used alone ascorbic acid is very slow in its action and has a long induction period. For this reason it is most often used in a super-additive mixture with Metol or a Phenidone derivative.
There may or may not be significant differences between the pictorial results of AA and HQ, but in respect to the above AA and HQ are very similar, at least for moderate pH levels.