I need to cut and shape a piece or two of pink insulating foam for a small hill. What is the preferred way to cut and shape this stuff?

Thanks for any replies.


Original Post

I use a razor saw to cut and shape pink foam. Hot wire tools also are sold for the purpose.


A hot wire knife is a great way to get the rough shape without making a mess.  The flip side is that edges cut that way are very smooth, not like something found in the natural world.  Once you are close you can rough up the surface many ways. I have recently used a combination of 60 grit sandpaper and dragging a pumice stone across the surface and really liked the final effect. 

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Have fun. FYI hot knives are readily available at craft stores like Joanne Fabrics or Michael’s.

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I have used an oscillating tool as well. It works well but it does make a huge mess. I would try to work over plastic or vacuum often with a shop vac. It takes a little while to get the hang of it.

Couple ideas...

Hot knife by Micro-Mark...et al.

Old set of electric oscillating/serrated carving knives.  Or, an old, dedicated long serrated blade 'bread' knife.

I say "old" on these, because mama won't be happy if you use her best cutlery from the kitchen.  Cutting foam accelerates dulling of the blades.  Sure, you can sharpen them again, if need be.  But home diplomacy will be enhanced if you get your own....garage sale, discarded (with spouse/parent blessing) kitchen tool, dollar store, etc....

And serrated knives will not create the fumes that a hot wire/knife will...requiring good ventilation!!!....but they will make some dust that an appropriate shop vacuum/filter will help control as the carving goes along.

I've used both types of the above knives on pink, blue, and beaded white Styrofoam.  They work well.



If you don't want to spend a lot of money just to shape a couple of pieces of foam, then a box cutter utility knife with snap-off blade sections is a pretty good choice.  Extend the blade as far out as desired to do your carving.  You can use spackling compound to fill in any voids and smooth the flat ground-to-hill transition if desired.  Coarse sandpaper or foam sanding blocks are good ways to smooth contours and rough up the foam surfaces before painting and applying ground cover.

A shop-vac is your BEST FRIEND when carving and sanding foam.  Don't even think of working foam without one !





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I have had bad luck with the hot knife. I keep burning up the wall wart. I use a large steak knife.... BTW, the fumes from burning foam are known to cause cancer and will make you ill so I tend to stay clear of this method when there is allot to do!





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Last edited by J Daddy

An old electric kitchen knife works well. So does a hacksaw blade. For carving details, use a Dremel tool with various grinding and cutting bits. Surprisingly, a cutoff wheel works nicely.




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I use a razor knife to cut the basic shape then I use a rasp to finish it off.  The only down side to using a rasp is that it does make a mess but it's easily cleaned up with a vacuum.  Have fun!


All great suggestions. Stay away from the hot knife due to the fumes. Manual or powered cutting blade works fine. I use a small compact ShopVac which is great for the hobbyist. Around $30.00 at Home Depot Shop Vac. Small enough to be mobile and I find that the power is more than adequate for its size.  ...just my 2 cents.

Last edited by Namvet4

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