Wood Stains
As the name implies, these stains penetrate into the wood rather than laying on top of the surface. These stains have the best clarity, showing the detail and markings of the wood best.
Example: Minwax Oil based Wood Finish
These stains are not as clear as penetrating stains, but offer better control of the stain color. These stains are highly pigmented and heavy bodied. Some of the stain remains on the surface of the wood, this helps in terms of controlling the color, but it can also obscure some of the details of the wood grain. These stains can be used over previously sealed or varnished surfaces - when properly prepared.
Example: Old Masters Wiping Stain
These are the heaviest bodied stains. Some of these can be used for "wood graining" with a graining tool and other specialty brushes and tools. The best of these stains will hold a pattern (that a wood graining tool imparts - for example), and are used as specialty stains. They can be used for bare wood staining as you would use a penetrating stain too. These stains, like wiping stains can be used over previously sealed or varnished surfaces (see label instructions).
Example: Minwax Gel Stain, Zar Wood Stain
- Shading Varnishes/Polyurethane
By tinting a clear coat (varnish or polyurethane), you can "shade" or adjust the color of a previously stained wood substrate. These are a all-in-one product - stain and finish together. These are the hardest to work with for color control, and in a general sense for getting good clean job. But, these products save time in toning and finishing in one step. They can be applied over previously stained and finished wood, with some exceptions (i.e. Polyshades should not be used over shellac or lacquered finishes).
Example: Minwax Polyshades