I don't know if you are familiar with Ron Pattinson. He is probably the foremost authority on UK brewing. Brad Smith has interviewed him several times on the Beersmith podcasts, Ron is a guest lecturer at beer events all over the world, the author of many beer history books and publishes the blog, Shut up About Barclay Perkins. One of his books called The Homebrewers Guide to Vintage Beer has this invert sugar recipe in it and I have used it faithfully for many years.
You will need:
- cane Sugar (not table sugar)
- citric Acid
- a candy thermometer
- a saucepan
The colors you are aiming for are:
- No. 1, 12-16 SRM
- No. 2, 30 - 35 SRM
- No. 3, 60 - 70 SRM
- No. 4, 275 - 325 SRM
This is what you do:
- For each pound (455g) of sugar you use, bring 1 pint (473ml) of water to a boil.
- Turn on the heat and add the sugar slowly, dissolving it.
- Add 1/4 teaspoon (1g) of citric acid per pound of sugar.
- Turn on the heat and set the alarm on the candy thermometer to 230°F (110°C).
- Stir frequently while it starts to simmer.
- When the temperature hits 230°F (110°C) reset the alarm for 240°F (115.6°C).
- Heat slowly until the temperature gets to 240°F (115.6°C).
- Lower the heat to keep at 240°F - 250°F (115.6° - 121.1°C).
- For No. 1 maintain the heat for 20 - 30 minutes.
- For No. 2 maintain the heat for 90 - 120 minutes.
- For No. 3 maintain the heat for 150-210 minutes.
- For No. 4 maintain the heat for 240 - 300 minutes.
I have made it with a simple candy thermometer, not one with an alarm, and just kept an eye on it. Most recently I have begun using a dutch oven cooker and just set my oven to 240°F - 250°F (115.6°C - 121.1°C). Making this on a stove top requires constant attention and adjustment of the heat to keep the syrup between those temperatures so the oven method makes things much easier. I have bought commercial invert sugar (Becker's is the only option available in the US) and I like the result I get with my homemade invert 1000% better.
I wasn't aware that Brad had included invert in the ingredient database. It wasn't there when I started making my own so I entered them into Beersmith manually.