I am staining a door and when I did the first side last weekend.. The stain matched other wood in the house beautifully. But when I went to do the other side this weekend.. The stain is much darker.. Even though I am using the same can? What should I do to lighten it up? What could have caused it to be so different?
I'm presuming below that you used actual stain, something intended to colour wood only, and not a finish-and-stain product such as "gel stain" which is a coloured varnish despite its (confusing) name.
What could have caused it to be so different?
I'm afraid we won't be able to answer this definitively for you because there are many variables. Here's a short list of what can affect a stain's colouring ability, one or more points may apply to your situation:
- Stain not stirred/shaken equally in both cases. Some 'stains' are coloured with pigment (not dye molecules) and as this is little particles they can settle to the bottom of the container.
- Lid left off between uses — solvent evaporates, making the stain more concentrated so it colours more strongly.
- Stain left on a little longer the second time — stain will give a darker result the longer it is left on the surface (within limits) so when two surfaces have to match it's important to apply the stain in exactly the same manner.
- Wood not prepped exactly the same on both sides — coarser sanding will generally make wood stain more darkly (larger scratches can hold more colour). Also, cross-grain scratches will give you a darker result than the same wood sanded with the same grit in line with the grain.
- Worn versus fresh sandpaper. The same grit can yield a different sanding result if fresh paper is used in one case and worn paper in another (or if by the time you are finished sanding the paper is worn). Worn paper leaves a smoother result and can additionally burnish the wood surface, both of which lessen the ability of wood to take stain.
- One side of the door was exposed more than the other so it wasn't the same colour to begin with, along with other possible effects*.
- The side that ended up lighter had a sealer or finish applied to it and the other didn't (or a thicker coat was applied to the first side) preventing it from being able to absorb as much stain.
Last but not least:
- Depending on how the door is constructed there's a very good chance each side is made from different pieces of wood, and with individual pieces of wood (whether solid wood or veneers bonded to any panel material) there is always the chance that they can take stain differently.
What should I do to lighten it up?
This can be very tricky to do. You should prepare yourself for the possibility that you won't be able to lighten the second side fully and may just have to live with it, unless you're willing to go through the process of completely stripping, scraping and sanding to get back to bare wood and start again from scratch. Fair warning, this is even more difficult and more of a timesuck than you're thinking!
One of the standard responses for this is to lightly abrade the surface but there's every likelihood that this won't be your best option here since you'll much more easily expose bare wood along edges and at corners compared to the large flat areas.
Depending on the stain type wiping down with an appropriate solvent may be the best thing to try, but there are no guarantees if or how well this will work (and again, the effect tends to concentrate on edges).
With an oil-based stain mineral spirits may still work if the stain hasn't dried for too long, if it has then try acetone.
If it's a waterbased stain you could try just water, but often you'll need to use an organic solvent to lift the stain once dry. Denatured alcohol may work, try xylene if it doesn't.
I think it's unlikely you used an alcohol-based stain but if you did the solvent to try is denatured alcohol.
*In addition to light exposure directly affecting the colour of the wood (often there is a slight bleaching while with some species, e.g. cherry, the wood goes a little darker and shifts colouring slightly), the side that was exposed more ages in a certain way, becoming less acceptant of stain than wood which was exposed to less air.