I also mixed the lye as part of the demonstration - it helps the safety talk when they see steam coming up off the mix, and if the group is small enough, feel the outside of the container (as Primrose does). Most people are thoroughly intrigued by the concept of an exothermic reaction.
..."The demo is an hour long, so plenty of time."...
You might find an hour will fly by, especially if you get a lot of questions along the way.
I've found announcing a dedicated question time for set points during the demonstration, with a final question/discussion time reserved for about 10 or so minutes at the end, allows people to just enjoy the demonstration. This allows you to fully focus on what you are doing (otherwise it is very easy to get sidetracked by interesting conversations/questions & answers - a 2 hours demonstration can be a little "chattier", but an hour will need to be a bit more structured).
People like handouts too - so if they have a page or two of notes and links, they feel like they have got value for money (it's a good way to advertise yourself too - you can include a business card and/or links to your website in the links section). Anything over about 4 pages of block text can overwhelm a person, so short and straightforward works best. If you include a recipe with a sample of your soap to take home, people get that whole "gift pack" feeling
I do pre-mix and melt my fatty ingredients ... having the ingredients on display works, but everyone usually only needs to see turn the hard fats and be told they are melted into the oils to get it (so that's a time saver). It does give you a key point (clear oils) to talk about.
I tend to take a dot-card with me for demonstrations (like for speeches) ... it helps me keep myself on track and not miss talking about any key points.
Pages of notes are of limited help while your demonstrating - it can be too time consuming wading through text to find where you are at, but they are good to have as a reference during question time.
I include a safety demonstration, but it depends on your audience how you approach that (mine includes a physical demonstration of how to wash soap batter of your skin, to show that your skin won't instantaneously fall off (some people actually think it works like that!) and then to demonstrate how to properly wash the batter off and what to look for (slippery skin) to tell if it's not been done properly. I don't necessarily recommend you do that for a formal audience, but incorporating some sort of memorable demonstration is good, to both combat the "wash with vinegar" nonsense that is all over the internet, and so they recall not to panic themselves when they eventually splash themselves
.
If you can bring a "wing man" with you, it can help enormously - having someone hand you the equipment or pass around notes can make the demonstration appear very professional (again, it depends on how formal your presentation and audience is going to be). Alternatively, I tend to lay out the ingredients and tools in order in front of me. If you are able to work from right to left, it looks visually more sensible to the audience facing you, but this isn't critical. Having the ingredients and tools lined up like that does mean that you have each step literally laid out in front of you ... the audience can follow what you are doing.
I like the idea of beer soap, but the problem with that is that you are introducing a more advanced technique that your audience can't go away and reproduce (easily) as beginners. The other concern with beer soap is that there are more failure points than a simpler soap, and if anything is going to go wrong, it usually happens in a demonstration (when you are already have your attention spread across more things that usual). I do rather like your idea of using local produce (in your instance, farm fats) for your demonstration - that connection to local business is invaluable in the setting. Perhaps a good compromise would be to demonstrate the farm type soap, and have the beer soap for a giveaway and talk about what you can do with more advanced techniques (it also gives you an opportunity to spruik your beer soap and advertise your links to the local brewery as well. Having those multiple ties to local business is an excellent idea when talking to a chamber of commerce group
).
Fundamentals - make sure you have power (safely - do a cord check if someone else has set it up for you), easy access to a sink (or have a bucket of water under the table for safety) and another bucket for dirty dishes (to safely get them out of sight and touch of your audience). Standard safety equipment, and a spare set in case you decide to engage one of the audience as your assistant
Pretties - at least one little swirl is impressive to watch and demonstrates how to separate batter and color it for swirling. An additive is another option - anything easy to spot in the finished soap is good. I would keep the fragrance simple and focus on the visual for a demonstration.
Having the same (or close to it) soap as a cutting demonstration always goes down well - it gives the complete story then.
If you have soap for sale, and it's allowed, bring some with you - almost invariably you will have purchase requests (in addition to your giveaways).
