I am making three two to three layer cakes and want to use the cardboard separators between the layers.  The lady who wants the cakes, does not like fondant, so I am using a shortening based frosting.  Will the shortening cause the cardboard to get soggy?  I plan to stack them about an hour before the event, but it may be a couple of hours before they are cut into.  I'm also trying to factor in 95 degree heat the same day.

Try wrapping the cardboard in tinfoil, it will prevent the cardboard from absorbing the moisture from the cake!

AAre you just referring to the cardboard rounds some people use underneath each tierrof cake? Probably not necessary to cover with anything, and I definitely wouldn't use tinfoil, wouldn't want little shreds to potentially come up with a slice of cake.

AI'm sure there's something I'm missing. But why are people always worried about soggy cardboard? I have never had a problem with this...or maybe I have and just haven't noticed.

^this.  it's just not an issue.

Thank you for replying.  The last cake I made for this family melted under the heat of the day.  I have heard of the cardboard getting soggy and I don't want to give this family another bad cake.

Oh I've seen references to people saving pizza delivery boxes, even DIAPER boxes to cut their rounds from.

if cardboards ever do get soggy it's from the moisture of the cake, not the icing, and it would take longer than a couple hours to soak them