So I just did a quick google search on the difference between H, F and B graded graphite pencils needless to say I figured out why my sketches are impossible to erase almost completely xD
For any other Traditional Artist Newbies such as myself this may help you out with sketches.
(H): pencils are hard and they leave less graphite on the paper. This means that they are lighter.
(F): fine Point. This is quite a hard pencil and is easy to keep sharp, but generally a bit too hard for general drawing.
(B): pencils are softer and leave more graphite on the paper, meaning they are darker.
- The more H's, the harder the pencil is. This means that a 4H is harder than a 2H and therefore, the 4H is also lighter. The 9H is typically the hardest and lightest graphite pencil available.
- An HB pencil is kind of in the middle. For drawing, it's still reasonably hard.
- The more B's, the softer the pencil is. This means that a 5B is softer than a 2B and the 5B will produce a darker mark. The 7B is the softest and darkest among common pencils, though you might come across an 8B or a 9xxB pencil as well.
Find out more here.