Support

Keep this site running.

Everything here is free and stays free — the eighteen unit-operation pages, the material compatibility data, the calculators. If it has saved you an afternoon and you would like to put something toward the running of it, this is where to do that. Any amount, once, no account needed.

Pay what you think it is worth

Give any amount

Handled by Payhip, which takes the payment and sends you a receipt. I never see your card details.

What it actually pays for

Small numbers, but they are real ones.

Hosting and the domain. The site is static and cheap to serve, which is deliberate — it means a slow month never threatens to take it down.
Keeping the numbers current. Standards move, membrane products change, and correlations that were fine in 2015 are not always fine now. Checking that is unglamorous and it takes time.
New unit operations. Each page is a model, a schematic, an animation and the writing to explain it. They take days, not hours.
Corrections. If you find something wrong, I would rather hear about it and fix it than have it quietly mislead someone.

Why give at all

There are no adverts on this site and there is no tracking beyond basic analytics. That is a choice, and it means the site has no income of its own. Support is what keeps it that way.

Other ways to help

Buy the workbook. The design calculator is a paid Excel file, and buying it supports the site directly. See what is in it.
Tell me what is wrong. A correction is worth more to me than a payment. Send it here.
Tell someone it exists. Costs nothing and helps most.

Nothing here is behind a paywall. Supporting the site does not unlock anything, because there is nothing locked. It just means the site keeps being here.