Well the sump pump at my house finally died after 20 plus years of service. After sitting under water for all that time I had to pull it out and replace it. That’s when I discovered all this great rust weathering material. The color is , well , real and it goes on my models just like weathering powder. 
Nice
Mike;
Not wanting to “rain on your parade,” but if you have access to an ultra violet lamp, you may want to bath the weathering supplies in ultra violet light for about 8 hours. After 25 years, there may be microscopic nasties living in that stuff. (I suppose a stiff disinfectant would work as well, but it may change some of the pigments.)
Just sayin’, David Meashey
Or you could bake the stuff in an oven for a while. Most nasties cant survive temperatures above the mid 100’s for too long.
Hmm, ya might want to run the Geiger counter over that.
I survived Covid 19 and the weathering rust will kill me . Can’t win (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif). Seriously it is gonna sit in this cup for awhile cuz I have nothing to weather right now.
So far my HOn3 layout has not grew anything that I used in the scenery construction over the years. This is because several trips to Colorado, New Mexico, and my Texas backyard I have scooped up many buckets of matter that I thought was questionably at times. I’ve always let it dry under the Texas heat and then stored in containers and sealed for years until it was needed, all being said, were all still alive here and none of us have grown any extra fingers, or things that I would call weird.
trainman