Using Isomalt To Make Windows For Car-Shaped Cake
Sugar Work By Bramsley Updated 10 Aug 2016 , 6:23am by Bramsley
Hi everyone.
I've been asked to make a very special car cake, and I thought I would like to make it so that it has windows you can see through to look at things inside the car. I thought I would use Isomalt to make the windows, but I have never used it before and am looking for some advice and a few answers to questions I already have.
The cake is needed for 15th July, but for reasons I won't bore you with, I have to make it in advance - at least a week, maybe more. I'll freeze the fondant covered body - I've done this before with good results so that doesn't worry me. The roof/windows shell will be made separately of Isomalt and fondant and will also need to be made in advance and kept in pristine condition.
To give added strength, I plan to make the whole roof/windows shell out of a single piece of Isomalt, adding fondant to give the effect of the roof frame afterwards. The car by the way is a Fiat 500L which has an roof top which is almost all sunroof, hence the 'glass' being needed on the top as well as the sides. The finished Isomalt needs to be clear and as thin as possible so that people can see the things inside the car.
My first and biggest problem is getting the right shape for the roof and windows. I think I will probably have to make a mold which is something else I have never done before. Would it be best to make a hollow mold that the Isomalt can be poured into and swirled around, or would it better to pour the Isomalt over the outside of the mold? Alternatively, can the Isomalt be poured flat and molded into shape around the mold afterwards? What is the best (ie easiest) way of making sure the edges of the shell are straight and level where it will sit on the car body? I would be very grateful to hear from anyone who has tried any of these techniques and can give me any advice as to the advantages and pitfalls to watch out for. Also, all advice on actually making a mold would be very much appreciated.
Once made, the next problem is storage. I understand spraying the Isomalt with a confectioners glaze will help protect it from the atmosphere and from becoming cloudy or discoloured, so I'll do that, but does anyone have idea of how long it will stay strong and clear once sprayed?
Fondant icing will be shaped around the Isomalt shell to look like the metal parts of the car roof. Will this affect the Isomalt in any way? I'm worried the fondant will eventually soften the Isomalt.
I'll keep the finished roof in an airtight container, but once the cake has been handed over to the client, are any special storage instructions needed? How long will the glazed Isomalt keep once it is exposed to the air?
I will be spending the next couple of weeks playing with the Isomalt nibs I have bought, to get some experience in melting and handling it, and also trying to make a suitable mold, either from existing containers, or making one from scratch.
Any and all advice on any aspect of making this cake would be greatly appreciated.
PS - if what I am planning proves impossible, or too ambitious, I will simply make the whole car out of cake and cover it with fondant which I have done before, but I really would like to give this one 'see-through' windows if at all possible.
Thanking you all in advance,
That's a really ambitious project if you've never used isomalt before. I've worked with it for years and I'd still be reluctant to make a large piece like that and store it for a week. How big is it going to be? Honestly, if it's a cake for an important event I'd do it out of fondant, as opposed to taking a risk with the isomalt. If I did do it out of isomalt I'd make three of them in case of breakage!
Gosh costumeczar, that's pulled me up sharpish. I knew it was going to be ambitious for me, but not that it might also be something an experienced isomalt user would think twice about. 
The isomalt piece would have been about 6 x 8 ins ( I haven't worked out the full dimensions yet, it may be more like 4 x 6 ins), and a couple of inches deep for the side windows and front and rear windows.
All the information I'd read online led me to believe that isomalt was pretty easy to work with, and that it would last for some time if stored properly. I'm pretty disappointed to learn that isn't the case, but thank you for the advice.
It's just the full logistics of it...The first issue would be pouring it into a smooth and precise shape, which is what you'd need for the windshield etc. I've done car cakes before and you have to get the shape and size exactly right so that the top sections aligns with the bottom section, or it won't look right. So for me getting the shape and the size right would be obstacle #1 since you're never 100% sure what size the cake itself will turn out to be once the fondant is put on it. Even if there's a 1/2" difference you'll end up having to add pieces to the car to fill in gaps and that won't look right if you want a very specific car.
Making a mold presents its own problems because you have to find a type of silicone that won't make the isomalt textured...It's a long story but the kind that doesn't make isomalt textured has a very fast cure time, so using it to make a large piece like you're describing probably won't work. Not to mention that you'd have to make an original of the car top to mold from, so then you're getting into working with clay or something to do that.
If you did manage to make a mold and pour the isomalt and it was sized perfectly, you then have to store it without breakage, which is the most dangerous part. If you're leaving it for a week you'd run the risk of humidity getting it and making it slump and get cloudy. I wouldn't pour the pieces until the day before I needed them, and even then I'd be super nervous that it wouldn't work. Doing a trial run is good to see if the piece is what you want it to be, but once that's out of the way you have to deal with the reality of the actual piece, and the risk of breakage is real...
Honestly, I wouldn't try it the way that you're describing. If I was going to do it I'd build individual sections of windows and pour the isomalt into those individually, then assemble them together ON SITE so that you don't have to move them. I looked at a picture of the car, and it looks like there are black sections around each window, so you could diagram those out so that each isomalt section had a frame around it. That could be done with a stained glass type method, I'll attach a video that I did to show you what I mean. Then you could build it like that. If you have some type of rigid framework inside the car top that you could attach all of the pieces to that would give it more stability, so you'd essentially be attaching each window section to a framework, does that make sense? It makes sense in my head...
here's the video link: https://www.youtube.com/watch?v=SLm2y2ofD2M
i'll tell you what I've done before that would be ridiculous to try for four windows and a moon roof - and I gather you want to pour this but --
I blew some up the size I needed and pressed a face shape into it -- to mold it -- but I used the whole thing --
I mean if you practiced and had the smooth molds - it is within the realm of possibility -- you'd need a razor point torch to trim it --
but like kara said -- worlds of expertise -- and made and applied at the last minute but there's a more expensive isomalt that is sturdier than regular isomalt -- some kind of pearls, can't remember the name more user friendly --
my mold was made of foam
venuance pearls or something -- I'm on my phone so im a little limited
i'm not finding them for sale -- they might still be out there but idk
Thank you both, costumeczar and K8memphis, for helping me understand where the difficulties lie.
I agree, making the mold was always going to be a problem, but I thought that by making a whole shell the final product would be stronger than having separate piece held together by a sugarpaste frame.
K8memphis - I have bought some isomalt nibs to play with. I wonder if these are the same as the venuance pearls you mention? The nibs are pre-cooked, can be melted in the microwave and are supposed to be less fragile and easier to work with than the crystals.
But, I accept that my plan was too ambitious. I could simply make the whole car out of cake and fondant, but I really did want to have things inside the car that could be seen. I may repost this as a more open question to see what other options people may come up with that might achieve this effect.
Thank you both for all your advice.
gelatin sheets? those are clear aren't they -- or gelatin you made into windows -- i have a book on it -- never got around to playing with it though -- probably some you tube videos out there --
when i was a kid we had candy that was like taffy and wrapped individually y'know like little bits of taffy are and the paper was clear edible rice paper -- that would be amazing -- never seen it since
Thanks for those ideas K8memphis. I'm going to look into using gelatin and will spend a day or two experimenting. If I can find a brand of that sells clear, unmarked gelatin sheets, and they don't go sticky or soften when exposed to the air, that could be a very easy solution.
I thought of just leaving open spaces where the windows should be, or maybe using a food-safe transparent plastic such as comes with shop bought gateaux, though I'd prefer everything to be edible (in theory at least)
I can't find any clear edible rice paper sheets for sale (Amazon have some but they are 'unavailable')
At least I've got the rest of this month to experiment with different options and see which work best and which keep best.
This cake must be made at least a week in advance, so the final solution needs to be able to cope with that.
Many thanks
Hi gscout3.
Thank you for your interest. In the end I used gelatin. After a few experiments I found that 4 leaves of gelatin to 1 tablespoon of water worked best for what I wanted - it allowed it to pour thinly enough so that the sheets didn't crinkle up but still set to a flexible sheet. I also found that pouring the gelatin onto a silicone sheet was useless - it just crinkled up and became unusable. It worked a lot better pouring it onto a large plastic lid. It stuck to the lid very tightly until I was ready to release it and then it came away easily and wrinkle free.
I made a mold for the car roof and used a couple of layers of modelling paste to set it hard enough and robust enough to handle. I used the same template to cut out window shapes in the gelatin that I used to cut out the windows in in the roof, just slightly larger so that I could stick them to the inside of the modelling paste frame. To make it easier to handle the frame, I left the top half of the side windows unstuck - this meant i could push my fingers under the roof to lift it on and off, and the gelatin just sprang back into place when I let go.
I've uploaded a couple of pictures for you to see how it looked - I was very pleased at the shine on them which made them look like glass. Apologies for the messy room in the background.
Thanks again for your interest and good luck with any similar projects you have in mind. [postimage id="4890" thumb="900"][postimage id="4891" thumb="900"]
That's excellent, you did a great job . The gelatin windows worked really, really well.
i bet the dealership would love to see this picture -- you did an amazing job -- love the windows -- wow excellent --
and gscout -- thanks for asking about the (awesome) results
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