There are way too many "experts" out there that have their methods. Some even write books. Maybe instead of writing books they should be doing the finishing. Some have their own products and are forum members and enjoy selling their wares. It's a jungle out there!!!
Some woodworkers experiment with different products and come up with mixes that serve their needs. IMO, one product will not do all variations, as there are different species, and differences in woods of the same species. What works on one piece may not work on the next. Generally, if all the stock came from the same source at the same time, I would guess that somewhere around 50% may be close enough to work the same. If they came from the same tree...maybe the same percentage.
So, what I'm getting at is that finishing takes practice and experimentation. Conditioning the wood for staining and finishing can be a very successful way to get an even blotch free finish. It could also be a disaster. Conditioning is simply a method of sealing the wood so the light parts of the wood will look like the dark parts. So, the soft parts will look like the hard parts. Sounds very simple...but it's not.
Pre-stain conditioners are basically a form of a sealer. What the variables are that not enough sealer will not produce an acceptable surface. Too much sealer will inhibit colorization. Using an oil base conditioner can enhance the grain with whatever oil content it's limited to in its mix. A waterbase conditioner will likely not change the color pre-stain. Using dewaxed shellac mixed with denatured alcohol could also work, but I'm not that excited in how durable shellac is as a basecoat for a finish.
So, basically, you can buy conditioners that are specifically for oil stains/dyes, and ones that are for waterbase stains/dyes. Then follow the instructions on the container and take your sample out to the final finish, which may be stain/dye and a clear topcoat. The sample will look different when stained/dyed, and then look different again after topcoating.
If you want to play with making your own, start with a general mix. For an oil stain, you could start with a clear oil base varnish 20%-25%, and the balance with mineral spirits.
For a waterbase conditioner, you could start with a waterbase clear polyurethane, with 20%-25% waterbase polyurethane, and the balance just plain water.
In doing samples, see how the stain takes and what the wood looks like. If it still looks a bit blotchy, increase the sealer component and/or, decrease the percentage of the balance. If it doesn't take the stain well, decrease the sealer component, and/or increase the balance.
Keep track of the ratios you start with. You can use cooking measuring spoons, or marked measuring cups. As a side note, you might just give a gel stain a try on a sample right off the bat (without a conditioner). On some species it may save you some shop time.
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