Rick,
I'm aware of some people who stains pamorblades traditionally here in Holland. Especially one person who wants to stay anonymous did the staining for me on some keris who needed it badly.
As Alan and Marcokeris said the results vary, especially on older blades. I was told that the result depended on the kind of materials that was used for the blade. Older blades where made with knickle contenting iron with very low nickle. Those blades have a more grey pamor appearance. Some blades need a week staining before the pamor becomes visible, other blades needed half an hour to get a result.
Sjors,
Just like Alan I stained a worthless keris blade once with sulphur to find out the result. The result was acceptable indeed, but that smell.....
You won't get permission from the mrs. to bring a keris stained with sulphur in the house. And if you get permission it will save you some money. Your friends won't come to drink a beer with you
.