Wood – Recommended pine dimensions for desk/shelf unit

Pine is a difficult wood to stain under the best of situations. Pine has areas of different density, color, and resin (pitch) content. Using a product like Minwax prestain helps a bit. Follow the timing instructions carefully when using a pre-treatment. Little tips: i like to apply a liberal coat of oil based stain with a sponge brush. Let it set a few minutes, then rub it in and evenly distribute with a lint free rag. As one rag becomes saturated with stain, I use a second drier rag to finish the rub in. The wetter rag is great for distributing the color. You don't want any really wet stain remaining on your wood after the rub in. Once you get to the urethane, sand lightly between each coat with 220 grit paper to remove any dust bumps. Remove all sanding dust with a slightly damp cloth, let it dry and apply next coat. Again, I prefer a good grade sponge brush, but a good grade regular brush for oil/urethane works good for appling the urethane. Remember, thin coats, and sand between each coat.

If I were making a desk 3/4" is the minimum that I would go on thickness. You could definitely go thinner with strapping under but I just like the look.

If you are worried about flex I would use the sag calculator. It is great and I use it when I build custom shelves. A desk should inherently have more support than a shelf but a desk will also have more load - so I believe the the calculations should be pretty close.