Manning Makes Stuff - Halloween decorations, paper mache masks, costumes, party ideas, and more

Manning Makes Stuff - Halloween decorations, paper mache masks, costumes, party ideas, and more

Working with foam board for art projects; cutting, painting, etc


Published by Manning on September 7th, 2015

I use foam board (aka foam core) in almost all my big projects — masks, Halloween decorations, etc — and I’ve learned a lot of techniques that help make working with it a lot easier.

First, check out my article about buying cheap foam board in bulk. I’ve found that the cheap stuff is much easier to work with, and it’s less than half the price of the good stuff you’d buy in an art store!

Cutting foam board

Of course for any project involving foam board, you’ll need to cut it into different shapes. It can be challenging to cut foam board into very precise, smooth, complex shapes, but I’ve learned some tricks that really help.

(Note: be extremely careful when cutting foam board! Always take your time, and never cut toward yourself. Foam board can be unevenly dense inside and the blade can jump a bit sometimes. If you’re a kid, get a grown-up to do the cutting for you; if someone’s gonna get sliced open, let it be them!)

First of all, a brand new blade for your X-acto knife is key. I try to be cost-efficient with all my projects, but one thing I’ve learned is that it’s worth the money to change your X-acto blade often. I used to use a blade for way too long, and my foam board shapes would come out really ragged and ugly. So change blades often and you’ll have way better success. Buy a set of five or ten blades and change them often. As soon as you feel like you’re having trouble getting a perfect line, change blades.

Put down at least two layers of foam board to protect your work area. I use any old scraps of foam board I have lying around for this. You can also use cardboard, but the corrugated lines in cardboard can cause your blade to veer away from the line you’re trying to cut.

Whenever you’re cutting foam board, always make sure your blade is going all the way through the whole thickness of the board. You don’t want to cut your shape and then find you can’t punch it out because a lot of little areas are still attached in the back. This is why those two layers of protection are important. Ideally you want your blade to go all the way through the piece you’re cutting and well into the first protective layer.

When cutting, it’s important to keep your blade straight up and down. If you hold the blade somewhat like you’d hold a pen, the line you’re cutting will have a diagonal edge. For most projects, you’ll be better off with a perfect 90-degree edge. It’s harder to achieve this, but it’s worth the extra effort. The main way I do this is to lay down on the floor and get my head down eye-level with the X-acto knife. That way you can make sure you’re poking the the X-acto knife into the surface perfectly vertical, and you can keep an eye on it as you cut, making sure it stays that way.

Another way to achieve this is to position yourself directly over top of the X-acto knife, so you can see that you’re looking straight down the knife. I do most of this work on the floor and end up getting myself into all sorts of weird yoga poses trying to get the perfect angle.

Again, never cut toward yourself. I try to cut slightly toward myself so I can see what I’m doing but in a diagonal line off to the side, away from me and most importantly away from the hand that’s holding the foam board in place.

Getting a near-perfect 90-degree edge to the shapes you’re cutting is really helpful for a ton of reasons. If you’re going to be building a complex three-dimensional shape with your foam board pieces, a 90-degree angle will help the edges line up nicely and help them be nice and strong when they’re taped or glued together. If you’re cutting multiple pieces of the same shape, the 90-degree edges will help all the pieces be the same size all the way around.

Of course, you may have a need for a diagonal edge on a shape you’re cutting, and this is easy to achieve by holding the X-acto knife like a pen. In my experience the 90-degree edge has been much more advantageous for all my projects.

If you’re careful to cut precise shapes with nice 90-degree edges on all your pieces, you’ll be able to construct surprisingly strong shapes with just foam board and packing tape. It’s a really satisfying feeling when you put all your pieces together and they form a nice sturdy shape.

Paper maché and foam board

I’ve learned some really valuable lessons from working with paper maché and foam board! For most of my projects, the foam board serves as an interior base along with other materials, and the paper maché doesn’t go directly on it. But for a few recent projects I’ve needed to apply layers of paper maché directly to large, flat foam board surfaces, and it turns out this makes the foam board warp! This can be a huge problem if you’re not expecting it, and if you need nice flat surfaces in your finished project.

When you apply paper maché directly to a large area of foam board, it goes on nice and smooth, but then a day or so later when the paper maché is dry you’ll find that the foam board has warped and curled a bit. This is most noticeable if you only put paper maché on one side of the foam board; the paper maché shrinks a bit as it dries, and this causes the foam board to curl up a bit at the edges.

If you apply paper maché to both sides of a large area of foam board, the paper maché will try to shrink on both sides as it dries, and this causes some strange, irregular warping all over.

Another very strange thing that can happen is that the paper maché dries and the board warps and you find that the paper has lifted away from the foam board entirely, creating a tight, drum-like surface! This was a crazy surprise the first time it happened to one of my projects. Here’s what’s happening: Foam board is actually three layers; a thick layer of foam in the middle with a sheet of paper glued onto each side. The paper is what gives colored foam board its color, but even white foam board has white paper on both sides. So, it turns out paper maché sticks to this layer of paper better than the paper sticks to the foam in the middle. As the paper maché dries and shrinks, it sometimes peels the paper away from the foam entirely! So you end up with a very curved sheet of foam, covered in a slightly less curved surface made up of the paper covering and the paper maché glued tightly together. There’s actually a cushion of air in between the two.

Obviously this warping and curving are a problem for some projects. There are a few ways to fix this at least partially.

One is to weight down your projects with books and other things. When I’ve got a warped piece of foam board and paper maché, I’ll leave it under a huge stack of books for a few days, and this helps flatten it back out for the most part. I’ve found that leaving the foam board with the rounded side up is more effective than leaving it with the curled edges up. The more books you use, and the more days you leave them on there, the better. You might not achieve perfect flatness, but it’ll be much closer.

In more extreme cases, like when the paper lifts away from the foam and creates that drum-like surface, I’ve actually sliced open the dried paper maché with an X-acto knife, flattened the piece out under books for a couple days, and then reapplied some paper maché. You might get some warping with this second round of paper maché, but much less than the first time. The downside with this technique is that your paper maché surface might be less perfectly smooth since you’re paper maché-ing over those sliced paper edges. Still, better than having the thing totally warped.

Painting foam board

I use lots of spray paint and acrylic paint on my projects, and both work great on foam board. However, if you’re painting directly on foam board, too much paint can saturate the outer layer of paper and cause the edges to curl up and detach from the foam interior as it dries, so watch out for that. If you’re spray painting the foam board, you can avoid this problem by not applying the spray paint too heavily; start with a fine coat of spray paint, and then when that’s dry do a second fine coat, and even a third, and so on, allowing it to dry completely between coats, until you get complete coverage. If you apply too much paint at once, the outer layer of paper on the foam gets saturated, and as it dries, the paper shrinks but the foam inside doesn’t, and that cause the edges of the paper to curl and warp. The same goes for painting with a brush, with acrylic paint, tempera paint, etc. The thinner you apply the paint, the better. Schedule yourself enough time to paint in thin coats, let it dry completely, and then continue.

Note for anything involving spray paint and any type of foam (styrofoam, foam rubber, etc): make sure to do a small test first! Spray paint will eat right through some types of foam and basically melt or dissolve it. I found out the hard way when I tried to spray paint a styrofoam pumpkin black — the spray paint instantly melted right through the surface. Anyway, the types of foam board I’ve used can handle spray paint just fine, however, it’s still worth doing a test before you accidentally ruin your whole project!

Consider removing the paper coating

For smaller pieces of foam board, you may be able to peel off the paper coating entirely, leaving you with just a foam shape. This will be less prone to warping, but a bit harder to paint and harder to paper maché. The foam surface is less porous than paper, but you should be able to get things to stick pretty well with enough time and effort.

The removable paper coating on foam board can also cause problems if you’re trying to glue two pieces of foam board together. The coating may peel away from one or both sides and the pieces come apart. So in some cases you’re better off removing the layer of paper before gluing pieces together. Another technique to glue two pieces of foam board together with a really strong connection is to wrap the foam board pieces entirely in paper maché, let them dry, and then glue them together (or even paper maché them together). This way the foam is locked in from all sides and nothing can slip or peel apart.

Creating curved shapes with foam board

It’s possible to create precise, strong, curved shapes with foam board using nothing but foam board and masking tape and then covering with paper maché. See my article about making foam board antlers for more info on this.

Wanna see some more things I’ve made with foam board?
Light-up voodoo sign
Foam board coffin
Fake wooden signs
Paper mache giant bat
Morgue drawers Halloween decoration

Have fun!

37 Responses to “Working with foam board for art projects; cutting, painting, etc”

  1. jane Says:

    you are talking about foam core not foam board. foam board is insulation boards made completely out of foam

  2. manning Says:

    Okay! The websites and stores where I buy them call them “foam board” or in some cases “foam core board” but I’ve seen the called “foam core” as well, the “core” being the foam in the middle, since these sheets have paper on each side. I suppose pure foam sheets wouldn’t have the paper layers but I haven’t seen those type of boards available where I’ve shopped.

  3. Crystal Says:

    Can u use plain black flat paint on foam board?

  4. manning Says:

    Hi Crystal! Yes you can; acrylic paint or spray paint or anything like that will work. A couple things to watch out for: Most types of foam board (aka foam core) actually have a layer of paper on each side, and these can curl and warp when they get wet, like from paint. You might find that the whole piece of foam board starts to warp a bit, or the paper surface can even start to peel off. Sometimes you can fix this by waiting for the whole thing to dry, and then putting a bunch of books on it for a few days to flatten it back out. That’s worked great for me. Good luck!

  5. Lamont Says:

    I want to paint large letters on black foam board. Is there a specific tape that I can use that will not damage the black paper?

  6. manning Says:

    Hi Lamont! There are a few brands of blue masking tape that are great for this; blue tape peels away very easily and shouldn’t damage the paper at all. Even regular yellow-ish masking tape would probably be okay, but the blue stuff is even more gentle. You can find blue masking tape at most big hardware stores and sometimes at art stores.

  7. manning Says:

    P.S. I like Scotch brand products; they make a blue masking tape that works great, but any other brand is probably okay.

  8. Steve Says:

    I’m looking at using a foam board to make a life-size Instagram page where there is a square hole cut out for folks to stand behind with props and posed for pictures. I’m looking at a 40″x60″x1/2″ foam board. If I cut a square hole, how many inches should I keep on each side of the hole so that the foam board doesn’t lose it structure/integrity if held up by one or two people?

  9. manning Says:

    Hey Steve! Good question, and I can only give you my best guess, but basically: At that size (40″x60″) if your foam board is 1/2″ thick I’d guess you’d need to keep about 6″ of width for your frame, but if you want to consider doubling up with two sheets (i.e. 1″ thick) I bet you’d be okay with just a 4″ thick frame.

    Another thing you can consider is reinforcing the edges of the frame with something sturdy like wooden dowels or very thin hollow metal rods — I’ve bought these in the “hobby” section of my art store; I suspect they’re for making objects for model train sets and stuff. Even a few wooden or plastic rulers from a dollar store would do the trick; just tape ’em in place along the back.

    Another thing you can do to make the frame sturdier is to run packing tape along both sides of it, and/or right on the edge. That will make the foam less likely to bend under a little bit of weight. Good luck!

  10. Sarah Says:

    Can I use washable paint on foam board?

  11. manning Says:

    Hi Sarah! I’ve never tried using washable paint on foam board; I’m sure it would go on just fine, but it may not be possible to wash it off, as the outer surface of foam board is a sheet of paper that’s glued on. If you tried to wash off the paint there’s a good chance the paper surface of the foam board would become mushy and fall off.

  12. Diane Says:

    I am using a large foam board bought T Hobby Lobby for a photo booth type project where the faces will be cut out for people to pose behind for pictures. One of your comments said to spray paint it lightly first before painting. Is there a clear spray paint I can use as a buffer before actually using acrylic paint to paint the picture itself that I have traced out? And what brand spray paint so you recommend? I am only considered the spray paint first because you said it might prevent the paper from curling up on the edges.

  13. manning Says:

    Hi Diane! Your comment made me realize my section about painting foam board wasn’t clear, so I just fixed it. What I was trying to say was: rather than apply spray paint (or any kind of paint) heavily to the foam board, it’s better to spray paint it lightly once and then lightly again, in order to avoid saturating the outer layer of paper with paint. The same would be true for any kind of paint; acrylic, tempera, etc. If the outer layer of paper gets saturated, the foam board may warp when it dries. There’s no clear spray (that I know of) that will prevent this.

    Beyond painting lightly, here are a couple things you can do: Use two sheets of foam board layered together, and use shipping tape all around the edges to hold them together; this will help keep them from warping; the two sheets are much sturdier than just one. Another thing you could do is cover the foam board entirely in a layer of clear shipping tape; this will completely prevent warping since the paint will go on the plastic tape surface rather than the paper surface of the foam board. It’s the paper that wants to warp as it dries.

    This stuff will help if you need to completely cover the foam board with paint. But if you’re only painting some imagery on the foam board and leaving a lot of white space, then warping isn’t much of a problem. Good luck!

  14. Cheyanne Anderson Says:

    Hey! I’m doing a styrogami project in my art class. I’ve decided to trace an outline on one piece of foam board, cut it out, and glue it to the other piece of foam board. The foam board that I am gluing on is black, and I would like to galaxy it with acrylic paint… could you give me any tips to help me out? I’m spending alot of time and effort on this project. I’d hate for me to mess it up.

  15. manning Says:

    Hey Cheyanne! I’m not sure I understand your question; can you give me some more information about what you want to do exactly? I can tell you that gluing the pieces of foam together should be no problem — I’d recommend Elmer’s wood glue (the only downside is it takes a few hours to dry), or a hot glue gun (much faster) — and it’ll take acrylic paint just fine. If you plan on covering a huge area with paint, like enough paint to saturate the paper surface, you might get some warping. But if you’re painting small pictures/shapes, you shouldn’t have any problems. Good luck!

  16. Adam Says:

    Hi, thanks for this article, I am working with 40×60 1/8 white non acid free foam board from Dick Blick. I’ve been painting on these with India ink as opposed to canvas it is much smoother and looks great. The only problem (aside from framing these monsters) is that I am afraid these artworks might deteriorate over time. It’s been a year already and there is no yellowing apparent yet. Still, do you think that these works could potentially lose value or turn horrific yellow? My hope is that with good treatment and no sunlight they will hold up for a long, long time. Any thoughts on my dilemma would be appreciated. I don’t even know how long this stuff has existed so who knows how long or well it will hold up.

  17. manning Says:

    Hey Adam! I wish I had any insights for you about this but I just don’t; any time I work with foam it gets covered with paper mache and/or a few coats of paint. I wish I could give you any more info, but I’d be Googling just like you. The fact that you haven’t seen a change in a year seems like a good sign, anyway! Good luck!

  18. Madeline Says:

    Hi. I just painted onto a huge (4’x10′) poster foam board. The acrylic paint didn’t stick, so I layered. I now have some pretty severe warping. Any suggestions as to “un”warp my board? I’m eventually going to hang them on a wall and would like them flat – or at least flatter than what I have now. I was contemplating painting the reverse side to see if it’ll warp back to original! Thanks.

  19. manning Says:

    Hi Madeline! I feel your pain. I think your idea about painting the other side might really help! However, I doubt it will perfectly flatten back out; you’ll probably end up with some big irregular dents and waves throughout the thing as the paint on both sides fights to pull the foam board in either direction. But I think it’ll end up closer to flat than what you have now.

    I would also try this, maybe after you try the above: Lay the foam board down on the floor with the more-warped side up (so the outer edges are as flat on the floor as possible and the biggest bump(s) in the middle are facing upward), and put a lot of books in the middle to push that part down to the floor. Wait an hour or so to let that settle a bit and then cover the rest with books as well; at 4’x10′ you might not have enough books to cover the whole thing, but you can spread them out evenly as best you can. If you leave it alone for two or three days like this, that might make the foam board almost flat, but maybe not entirely flat. With smaller pieces (like 2’x3′) I’ve gotten them almost perfectly flat this way. The more weight, and the longer you leave it alone, the better. Good luck!!!

  20. john Says:

    Madeline,
    You could try criss cross cuts through the the back paper where required until it settles flat. Then glue onto another sheet of flat board to support it. 4 x 10 is pretty hard to deal with though, try it on something smaller first maybe.

  21. manning Says:

    ^ This is a great suggestion!

  22. Andrew Johnson Says:

    Hello. I’m planning on testing some spray paint on some foam core materials this weekend and seeing if anything warps, but basically my project I am thinking of is going to be kinda 3d. I wanted to cut out shapes from foam core (because it seems like the easiest material to cut how I want without any tools or taking material to get professionally cut) and then essentially layer these different shapes onto a canvas and create a kind of three dimensional piece with circles, squares, and triangles on top of each other. My original idea is to spray paint because I want to create gradients easily, but I’m just worried about warping. I will be painting all sides except a back side as that will be secured to the canvas or on top of other shapes.

    I haven’t tried yet any of these techniques, but have you heard of putting a coat of non-water based polyurethane minwax on the paper side of foam core? I was watching a video on painting model planes. The material seemed to be designed out of foam core and the person mentioned putting a coat of of the polyurethane minwax on top of the paper side and that helped add a layer of water proof protection for painting.

  23. manning Says:

    Hello Andrew! A few things… The smaller the piece of foam board, the less likely it is to warp, especially if you just use one or two light coats of spray paint. So if you’re using pieces of foam board that are, I dunno, eight inches or smaller, there’s very little risk of warping from the spray paint. However, if you really saturate the outer paper layer with lots of paint, the paper layer on the outside of the foam board may curl up a bit. You could also avoid this by wetting the foam board and peeling the paper layer off, but then I’m not sure how well the paint will stick to the foam; it’ll probably work fine! But you’re right to do some tests. Any warping is the fault of the outer paper layer; the foam inside doesn’t want to warp at all, no matter how much paint you use.

    I think with any kind of sealant you’d have the same situation — if you apply it lightly nothing will happen, and if you saturate the paper layer too much it’ll curl up. I’d love to hear how it all comes out! Good luck!

  24. Ariel Says:

    Hey Manny. We are building a stage and want to warp the foam to kinda round out around the musicians and stage. We are using very large thick sheets of white foam because we plan to project visuals onto the foam as well. any idea’s on how this can be done a bit easier and a little quicker? pleasee! we also plan to cut a logo out of the foam.

  25. manning Says:

    Hi Arial! I don’t have a definite answer because I’ve never worked with thicker foam, but here’s an idea: If you’re able to gently curve the foam sheets in your hands, you can block them between the wall and a table or something like that, so they’re held in that curved position, and then apply lots of tape on the inner surface of the curve — Scotch heavy duty shipping tape works best for this. That might be enough to hold the shape. If not, a few layers of paper mache on both sides should hopefully do it.

  26. Cynthia Fuino Says:

    I am giving a baby shower and I’m considering using foam board to create baby blocks to use a centerpieces. My concern is that I will not be able to cover the visible edges of the foam board. I need it to be pink and I’m thinking I will spray paint it. Is there a specific glue I should use to attach them? Or should I just find another medium to use other than foam board

  27. manning Says:

    Hi Cynthia! I totally hear you about the edges of the foam board. Spray paint will cover the edges, and with the foam board and paints I’ve used I’ve never had a problem with the foam melting (it’s happened to me when working with other types of foam shapes, but never with foam board/foam core). However, the painted foam edges will still have that rough texture of the tiny bubbles in the foam, unlike the big flat surfaces, which are coated in paper. The only solution I’ve found to hide these rough edges is to cover the whole piece of foam board with paper mache, to unify the texture all over. That’s a lot of work just to hide those edges; you might be satisfied with how they look after just spray painting them.

    You might want to try a coating or two of gesso (either the spray kind or brush-on kind) to smooth out those edges a little more before spray painting, but I’m not sure this will smooth them out perfectly.

    Any kind of glue will work! Tacky Glue, Elmer’s wood glue, and hot glue are all perfect for this.

    One more thing, make sure you use a brand-new X-acto blade when cutting so you can get the edges as smooth as possible! Good luck!

  28. Vicky Herman Says:

    I want to make faux beams in my living room. What would be the best to paint with? I will be using the pink or blue styrofoam sheets.

  29. manning Says:

    Hello Vicky! I’m jealous, I’ve wanted to do that for years! So, I’ve never used the pink or blue foam sheets you’re talking about, but I’ve got some ideas for you: First, I’d try dark brown spray paint on a piece of scrap foam and see if it melts. If it doesn’t melt, then spray paint is probably your best bet! You can paint, let it set, and then finish it with matte spray (for a raw wood look) or gloss spray (for a laquered wood look). If the spray paint melts the foam, then I’d use acrylic paint with a big paintbrush. Acrylic will definitely do the trick but it’s a lot slower than spray paint.

    The way I’d wanted to do fake beams for my apartment would’ve been this: thin sheets of foam board, cut out and taped together to make long hollow box shapes, and then I’d cover them completely in paper mache to hide the tape and unify the texture all over. Then I’d do spray paint and probably matte spray.

    Good luck!

  30. Crews Says:

    I got a lot of information about this and I am going to at least try it several times.ha ha ha I see some of this yes!!!). Foam board as labeled in this store and my my has been going crazy thinking about the endless possibilities with this particular item…thank you…

  31. Molly Born Says:

    I am trying to make a back drop sky for a model train layout. Today I painted 2 of the pieces and they both curled. One more than the other. In reading one of your comments where you explained that putting the paint on too thick will cause that to happen. If I paint several layers very thin, letting each layer dry before adding another layer, will that work? Thank you for your much needed input!

  32. Ashutosh Says:

    Hello! I want to plaster the foam board model and then later sand it! Can you please help me out and suggest what material can I use to plaster the foam! Thank you!

  33. manning Says:

    Hello Ashutoth! I’ve never done exactly what you’re talking about, but if I wanted to try something like that, I would use Elmer’s Wood Filler. It’s a clay-like substance that’s basically wood dust and glue. You can spread it on really thick and sculpt it a bit, and when it’s 100% you can sand it. It’s normally used for things like, for example, filling in a deep scratch in a wooden door — you spread the wood filler into the gap, let it dry, and then sand it smooth. It’s really fun to work with, and I’ve tried using it in some paper mache projects, but never to completely cover a sculpture and then sand it. My only concern would be that if you spread it on too thin, it might crack or break as you sand it. Good luck!!

  34. Michelle Says:

    Hi Manning,
    I have acquired several large framed paintings over the years but now am moving and want to transport them safely. Two pieces are 42” x 58”. I would like to use foam board to prevent anything from touching the painted surface when I box them up for the movers. However, I am having trouble finding art store foam board that is big enough and thick enough. Can I use foam insulation board from the hardware store? I can get boards 4’ x 8’ that are fairly thick. What do you think?

    Thanks so much for your time.

  35. manning Says:

    Hi Michelle! This is definitely outside my area of expertise, but I think you could use foam insulation board to protect paintings. I think the foam would work great; my only concern would be anything that’s touching the actual surface of the paintings; you might want to cover the painted surfaces with wax paper or something to protect them from anything sticking to them. I’d be a little concerned that the printed surface of the insulation board might stick to the painted surfaces a bit, especially if they’re in contact for a long time, and/or in hot weather. Good luck!

  36. Portia J. Vanlong Says:

    Hey All,

    I saw this op youtube and tried with great results: spray bottle ( they used a paint brush however), room temperature water, lightly sprayed the back side of foam board previously painted with my design. Dried it with a hair dryer, and it totally”un” warped my work. I was thinking about using a little spray starch if this doesn’t not give me permanent results. Anyone ever tried starch to stop warping? Love to hear about it!

    Peace!

  37. manning Says:

    Hi Portia! Thanks so much for this! I will definitely try this method. I got lucky with a piece recently too: I painted one side of a big foam board sign — like, I painted the entire surface of one side — and it warped quite a bit as it dried, but then I had to paint the other side too, and when I did that it totally straightened itself back out! I was really surprised with how well that worked. I’ve never tried starch but now I wanna try that too!

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