Complex sentence: Dr. James Stark was a chemist during the 1800's who experimented for 23 years and had tested 229 recipes for their durability on various kinds of paper to find the most stable iron gall ink recipe.
Split into simpler sentences: Dr. James Stark was a chemist during the 1800's who experimented with ink recipes for 23 years. He tested 229 recipes for their durability on various kinds of paper to find the most stable iron gall ink recipe.