After pulling off all of the 1970's panelling throughout our 1916 farmhouse, we've had to patch the multitudes of nail holes in the plaster walls which will require floor to ceiling sanding. As I was concerned that the original paint under the panelling contained lead, I purchased a lead testing kit at the local hardware store. I've tested four different rooms, and all of the tests were negative for lead. However, I've since been reading that any house built prior to 1950 will always contain high levels of lead in the paint, so I'm wondering if these tests are reliable and am I okay believing we're lead free?