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Shelf life of rainbow sponge
I've baked two 8&6 inch rainbow cakes early today and the customer is wanting to collect it Saturday to cut Sunday. There's quite a bit of work involved so I was planning on icing it tonight and decorating tomorrow. Will it still be ok for Sunday as I was wondering whether rainbow sponge would dry out quicker as the layers are a lot thinner. Used my normal cake recipe which always lasts well.
You could just brush a little simple syrup on each layer, that would definitely keep it moist. Once you've got the filling in and covered it will keep fine. Make simple syrup with equal quantities of sugar and water, boil for a minute of two, cool and brush on each layer before filling and stacking.
Hope this helps.