Bomb making requires the "Bomb Preparation" skill (a silver Intelligence talent), so Geralt can not make bombs until he reaches level 15 at least (and then only if it is really a priority as other talents are much more useful). He can, however, use any bombs he finds. Bombs require alchemical ingredients, just like potions, but the bases are different. All bomb-making bases are referred to as "black powder" irrespective of the actual colour of the item.
Top quality bases[ | ]
Buy Sell 
Zerrikanian mix 40 
8
Alchemist's powder 70
14
- Only Dragon's Dream requires a top quality base.
High quality bases[ | ]
Buy Sell Saltpeter 10
2
Stammelford's dust 20
4
- All bombs except Dragon's Dream require a high quality base.