Good morning!

I use a swiss meringue buttercream for all of my cakes but I am running into a problem and would like to know why it happens. When I ice my cakes, I put them into the freezer to set up for a few minutes, pull them out and smooth with a knife dipped in hot water and wiped off. I have notice that the colored icing kind of gets mottled a bit, but it has never been a big deal. The other night I had a beautiful white cake and when I started smoothing, the icing started changing to an awful yellow color.

What causes this, and what are the solutions? I feel like I am missing something obvious, but I can't figure out what. Any help would be appreciated!

It seems like your icing is simply melting due to the hot knife. Once butter melts it is no longer the same beast as unmelted butter. Your icing will seperate also.

I use IMBC and I would not use a hot knife on it, especially colored. For lack of a more scientific explanation....it is like when you melt butter to use for anything....it will never be the same. The coloring also likes to hold on to the "fat" from the butter, so those bits will be darker...and other parts become lighter. It will get mottled.

Is the freezing/hot knife method the same one you have always used? I try to just smooth as best I can with my bench scrapers, and once it is hardened up I sort of "shave" anything that is not smooth enough. But I quit trying to hot knife it.

Thanks so much!!

I used to use a crusting buttercream, so I never had to worry about this. I also don't do a lot of white cakes, when it has happened with colored icing it is usually not a big deal and sometimes looks cool. I just about died though when this happened to my nice white cake!

I actually tried the scrape method today and that worked well. I also tried to smooth the icing with a gloved hand, but that also changed the color. It's like any amount of warmth changes it.

How do people use the hot knife method though without this happening? I have seen so many blogs and people here utilize that method, but couldn't find anything with a search about the color change?

A hot knife or spatula will discolor your SMBC. To get a really smooth finish, pipe it on your cake, smooth it best you can, then pop it into the freezer for 15 minutes to quick chill it up. Then use a bench scraper or large puddy knife (that's what I use) and scrape the sides and top. But even this can discolor your buttercream if your scraper is warm. If this starts happening I dump it in a glass of ICE water, then wipe it on a towel and keep scraping.

Jen

Do you know the science behind the color change? Why doesn't American buttercream do the same thing? The butter can't be the reason, because most other buttercreams have just as much.

If you look in my pictures at the leaf cake, that cake has the discoloration you're talking about. My wedding cake did too. Both were iced in IMBC. I used the hot scraper on those and I think that caused the problem. From now on, I'm not applying any heat-just using the icing when it's really soft and super scrape-able.

All, I am also so desperate with this discoloration on SMBC..

Anyone had tried Jen's techinique keeping the scraper cold with ice?. I did not use hot knife but scrape it while the cake is cold but still with the colored SMBC, you'll get the streak!..

I would love to try with Jen's tip with ice the scraper. So please if anyone tried it, let me know. thanks!!