Never heard of Royal Icing.

Also see.

G’luck!

I would add the whites to the sugar and then stir in the water one tbs at a time and just watch the consistency. You might not need all the water with whites instead of the powder.

The simplest answer would be to abandon your “powder” recipe and use a recipe that calls for real egg whites. @ibstubro linked one; you can find many more with a Google search.

Alternatively, you can convert the meringue powder to egg whites, then work them back into your recipe. According to this website, “Three egg whites equal approximately 3 tablespoons meringue powder plus 6 tablespoons water.”

Using that formula, I suppose you would use 3 egg whites and no water in your original recipe. It’s not a perfect substitution, because your mixture will still contain 1 tbsp of water too many. But then, this is just one substitution – there are bound to be others.

Thanks for all your answers. Problem solved, the missus took over the royal icing duties while I was out running other errands.