This is a beautiful drawing Patricia! As you make colors darker and more saturated you also have to darken the areas (in various stages of shadow) that you have all ready toned. For example, if you put a layer of a reddish brown on top of your existing drawing you would still see the range of tones and the branch would retain the form you established. As you add more layers of reddish brown, it will start to cover up the original toning so you have to keep adding more tonal color(in this case probably dark sepia) to retain the range of shadow tones. Remember not to lose your highlight, which you can probably leave as is.
This wood is actually much darker than it appears here. How do I darken it without losing the shading?
This is a beautiful drawing Patricia! As you make colors darker and more saturated you also have to darken the areas (in various stages of shadow) that you have all ready toned. For example, if you put a layer of a reddish brown on top of your existing drawing you would still see the range of tones and the branch would retain the form you established. As you add more layers of reddish brown, it will start to cover up the original toning so you have to keep adding more tonal color(in this case probably dark sepia) to retain the range of shadow tones. Remember not to lose your highlight, which you can probably leave as is.
Lovely, Patricia. Do what Doug said 🙂