Any thoughts on this one...last 2 stacked tier cakes I have done...6 on 8...I notice hairline cracks. Not doing anything different...put bubble straws between the layers, 1/4 inch thick covered board, same icing, etc...so frustrated. Any thoughts...

Yesterday I had a gas bubble on the one side...haven't had that for a bit...not sure what that was all about, but anyway. More irked by the hairline cracks...

Any ideas, help?

Was the fondant to dry? You could fill in with buttercream.

Dunno - hairline cracks frequently indicate that your support boards are flexing or sagging. You didn't say what your boards were made of, but cardboard will absorb moisture and/or grease and will not properly support your cake. The air pockets just seem to develop sometimes as the cake settles.

It was all buttercream...no fondant...
My cake boards are 1/4 inch thick particle board that are foil covered...

Thinking it could be one of two things...the bubble straws I used weren't cut evenly (maybe one a little higher than the other), or, the cardboard disc I used between the layers...I have the bakery waxed coated ones...coated on one side, but cardboard on the other...I put the cardboard side down on the under side and put the cake on the coated side...could that be the problem possible...the cardboard on the underside is breaking down maybe? This is happening on a 6 inch 2 layer on an 8 inch 2 layer...any other size, I would use the pillars and plastic seperator plates.

Thoughts?

I use the same boards as you and put the cardboard side on the bottom cake and have never had cracking problems. The only time I have had a cracking problem is when I have put a heavy cake on a thin board (1/4"). Then I go to move it and get the cracks and it drives me crazy. I now use a thicker drum board (1/2") for cakes of that size. Any of my tiered cakes or larger shaped cakes get a drum board and I have never had any issues.

okay...so maybe that is it...I should put the white/coated part on the top of the bottom layer and the brown uncoated part under the bottom of the top tier. I'll try that next time...kind of makes sense. Was starting to get really frustrated, and hated the thought of going back to plastic divider plates and columns...too pricey.

It could be from excess movement. What size board are you putting the 2 tiers on. That board needs to be thicker than a 1/4 in. Also are you frosting the cake while the cake is cold/frozen?That could contribute to it.

No, i never refrigerate my cakes or freeze them...
I am horrible with measurements...but actually the board is 1/2 inch thick. I've used these boards forever, so I know it is not the board the whole cake is on...something either with the cardboard between the layers, the bubble straws or my icing (and not sure it is that).

Since you are using the thick boards, I wonder if the icing could be too dry? I know moisture can cause a lot of issues with icing. I have never used plastic plates or columns. Although I have never used the bubble straws either. I always use wooden dowels. I just bought my first bubble straws today to try.