Woodworking and Catholic thought

While scraping and sanding two window sashes that will be re-stained and re-varnished, I noticed that it's nearly impossible to get all the old stain out of the wood. Scraping is like going to confession: the surface junk comes off, but the stain remains. Purgatory (that merciful doctrine) tells us that all the deep-seated stains, come from years and decades of sin, can be and are removed; probably very slowly and painfully, but with the promise of heaven when we're purified enough to go there. I suspect that for most humans (me especially) the deepest stain is an attachment - sort of a deformed affection - for our favorite sins. That is what needs removal the most.