Regarding baking time. Bake to internal temperature NOT time. The internal temperature is important because it determines how much water evaporation has occurred inside the cake. That tells you how dry your cake is inside. Time on the clock can’t tell you that. What the clock does tell you is when to check the temperature of the cake.

Approximately 10 minutes BEFORE the stated done time on the recipe look at the cake. If it had risen to the top of the tin or close to it AND it looks set in the center, lightly touch the center of the cake. If the finger imprint remains, continue baking and perform the touch test every five minutes.

If the finger imprint springs back up, then use an instant read thermometer to check the internal temperature in the CENTER of the cake. The spring touch test is a good gauge to check the internal temperature.

Bake to an internal temperature is between 96°C (205°F) - 100°C (210°F).

Do not let the cake reach a temperature beyond 210°F (99°C). Beyond this temperature too much water will evaporate and the cake will be dry.

Also if your baking tins are dark metal reduced the oven temperature by.15°C (25°F). The dark color coating on the tins conduct heat much more intensely than a natural metal cake tin. The batter in contact with the metal will bake and set way faster than the center. This produces a cake with a very dry, thick tough crust and a dry crumb in the center.

Carrot cake is notorious for sinking in the middle. 325°F (160°C) is a better baking temperature to allow the batter in contact with the metal to bake more slowly and keep in better time with the center.

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Step by step instructions to scale a recipe.

Step 1: find the radius by dividing the diameter of the tin.

20 cm tin / 2 = 10 cm

30 cm tin / 2 = 15 cm

Step 2: Square the radius (r²)

10 cm x 10 cm = 100

15 cm x 15 cm = 225

Step 3: multiply the r² by Pi

(Pi = 3.14)

3.14 x 100 = 314 (area of pan in recipe)

3.14 x 225 x 1 = 706 (area of pan you want to use)

Step 4: Divide the area of the pan you want to use into the area of the pan in the recipe.

706/314 = 2.248

Round up to 2.25

The multiplier is 2.25.

Multiply the amount

of each ingredient by the multiplier. So if the original recipe for the 8 inch cake called for 250g Flour multiply it by 2.25

Flour 250g x 2.25 = 562.5

Use 562g flour for 12”/30cm tin.

Note; this is for scaling recipes for tins for the height. If the height of the tins are different, there is an added step that I did not cover here.