Agar Gelling Percentage Amount Calculator

Agar-agar gelling by percentage

Agar-agar is a polysaccharide (agarose + agaropectin) pulled from red algae (Rhodophyta, mostly Gelidium and Gracilaria). You dose it as a percentage of the liquid's mass. The usual formula is massagar = liquid (g) × % / 100, and most recipes sit in the 0.5-2 % (m/m) range. At about 0.5 % you get a soft, brittle jelly. Push it to 1 % and you land on that classic dessert texture; 2 % gives a firm gel that holds up to cutting and works for gel-clarification.

What makes agar odd is its thermal hysteresis. It sets at 32-43 C and won't melt again until you get above ~85 C. That gap is far wider than gelatin's, which is why you can serve an agar gel warm and it stays put. Bloom the powder in cold liquid first, then bring it to a full boil and hold it there for a minute or two so it hydrates all the way.

Applications

In modernist kitchens agar shows up everywhere, from fluid gels to hot jellies to gel clarification (the technique took off thanks to Ferran Adria's elBulli). Japanese cooking leans on it for kanten and mizu-yokan desserts. Microbiologists reach for 1.5 % agar as the standard way to solidify culture media in petri dishes. And for vegan or vegetarian cooks, it stands in for animal gelatin (collagen).

FAQ

How is agar different from gelatin? Agar is vegan, firms up at room temperature, and stays solid all the way to 85 C. Gelatin (animal collagen) needs the fridge to set and melts in your mouth around 35 C.

Why does my agar gel not set? Usually the mix never hit a full rolling boil, so the agar didn't hydrate. Very acidic liquids (pH < 4) weaken the gel too, so bump up the dose or buffer the acid.

Can I remelt and reset an agar gel? Yes. Heat it back above 85 C and let it firm up again. Unlike gelatin, agar handles several of these cycles without losing much strength.