David Siskind | Sunday, 28 December 2025
Last week I wrote about teachers and that none of mine were memorable as mentors nor examples. But, yesterday, out of the blue I gratefully recalled an impactful someone I hadn't thought about for years, Mark Freeman. I would have to call him a mentor. We both worked for Dorr Oliver, an engineering company emphasizing liquid/solid separation technologies of various types - phosphate mining thickeners, cornstarch wet milling centrifuges, papermill fiber screens, also offering unique fluidized bed solids reactors and calciners. Mark was a plasma physicist, I’m recalling a Berkeley PhD but am not sure. He was very tall (6’6” or 6’7”) and an exceptionally loud talker. Our project was in rural Georgia. We were working in Gordon and dining there and in small nearby towns, Ivey, McIntyre, and Milledgeville (Georgia’s capitol during the civil war). Gordon, Ivey and McIntyre had a common 50 page phone book - many residents were listed by their nicknames (“Key-man Turner” for example). This was truly “country.”. We would walk into Mildred’s in Milledgeville for a barbeque lunch, and his noise and size would turn heads. I was mortified but people there loved him.
He seemed brilliant to me. I think that was right. He was certainly charismatic. He had great math skills and was a hands-on experimenter. He was in his early 50s. I was a year or two out of school. We were working together on an “electro-filter” for the separation of colloidal kaolin clay from water - a key step in the mining and refining for a mineral that is the main ingredient in kaopectate, also used in cosmetics, as a brightener for high quality paper, and for insulators of various types. Kaolin is a bright white clay and was mined in the 1970s in big open pits primarily in Southern France, Australia, and Central Georgia. The “electro-filter” was an electrophoretically augmented vacuum filter that used an electric field to limit the blinding of a filter cloth used to separate suspended solids in a clay slurry from water added during the mining process. The slightly charged clay particles were driven away from a cathodic filter cloth toward an anode. It was designed as an energetically efficient replacement for a thermal evaporative process. But the devil was in the details - the process generated hydrogen and chlorine gas, corrosion of submerged parts was a big problem, but most critically, the scraper for removing clay solids deposited on submerged anodes was unreliable. Our first full-scale prototype did not work well and the concept was never embraced by the mining companies. Still...
Mark was always amazed by what I didn’t know and how little my engineering education emphasized laboratory work and self-discovery in general. I only worked with him for 6 months, maybe, but looking back I feel that he had a huge impact on my work and my choices. He taught me about the value of experimentation, about controls and pilot facility design but most importantly how to lean in, try things and grind. And to that end he introduced me to McMaster Carr, then a catalogue house, now maybe the best designed web-based industrial supply catalogue on the planet (click the link and explore, please). And that you could live out of a suitcase if you had to. I only knew him briefly but I know he changed the trajectory of my working life, orienting me toward adventure and acceptance of risk. If it weren’t for Mark I would probably have worked in a cubicle my whole life. Instead I found myself swinging from ropes from ships to oil platforms, snowshoeing through abandoned mines in the Sierras and developing and testing meteorological measuring instruments in the California desert.
Mark Freeman died young, shortly after we worked together. I had forgotten him. But now remember and understand that you meet your teachers when and where you find them. Instructors have an impact way beyond the subject they are teaching. Even if they only engage the student briefly. Excitement about a topic is contagious and immersive exploration can lead to a lifetime of corollary effects. So here I am. One thing led to another and tomorrow I’m off to Malaysia to spend a little over a week with Paul. I think I practiced well. We’ll see.
On the Christmas Rain. We go a few inches here and the LA River peaked at 10,000 cfs, more than 100 x its normal flow. This will have rolled some big rocks and reconfigured many of its islands. I won’t get to look at it until February but it will be different.
Happy New Year.