Testing Cleaning Solvents for FOAM-iT
I’m working on my next robot and need a sturdy, but very lightweight material for the body. I came across Smooth-On’s FOAM-iT Series of castable, rigid urethane foam and felt it would be a good fit for my needs. I chose FOAM-iT 4 to get the balance of rigidity and weight I was seeking.
In a nutshell, this is a 2 part formula that, when mixed, create an exothermic chemical reaction that rises and fills a cast. One of the key challenges with this material is that it is VERY sticky and sometimes difficult to remove from tools or the mold during clean-up. Because of the size and shape of my mold, I chose plywood for the cast material – an especially challenging material. There is a lot of discussion on other forums around the Internet with opinions about the best option, but I needed to test for myself. So, I’m writing this blog to document the testing I did in hopes it will help someone else in the future.
Cleaning Solvents Tested
- Acetone – Seems to be a favorite among professionals for expanding foam clean-up. I found lots of stories about it discoloring or weakening surfaces, so I was a bit nervous about working with this stuff – it sounded quite strong.
- Mineral Spirits – I had some on-hand so I thought I would give it a try. I’ve used it for years to clean brushes, but it was not mentioned on any of the internet forums. My inclination was that this was weaker than Acetone, and probably would not work well. BTW – the product name may sound like an adult beverage, but it is not!
- Motsenbockers Lift Off – I read about this stuff online and it seems specifically designed to do what I needed. I was also liking the fact that it seemed to be environmentally friendly and less harsh than some of the other options. There are several interesting videos online demonstrating the product, but they made me skeptical since they only demonstrated on wet foam, and not try foam. I was able to find a small bottle (4.5 fl oz.) to try so I did not have to spend much.
- Goof Off – I read about this stuff online also, and thought I’d give it a try. Again, it seemed specifically designed for what I wanted to do, so I was optimistic. I was able to find it in a small can (4 fl oz.) so it was not expensive to test.
- Goo Gone – I had some on-hand so I thought I would give it a try. I’ve used it successfully when trying to peel labels off to get rid of the adhesive residue, so I know it has good cleaning power.
Initially, I tested by applying the cleaning solvent directly to a block of dried foam. In all cases, this had zero effect. Lift Off and Goof Off specifically indicate that this is not the intended use of the product and it will have no effect. Still, I wanted to see what something as strong as Acetone would do to a block of dried foam. To hear folks talk about this stuff online so reverently, I had an indication it was going to be something like a scene out of the movie “Who Framed Roger Rabbit” where they put Toons into the “The Dip” chemical vat. Alas, this was not the case at all!
No!! Not the DIP!!
I assembled some tools and plywood forms that were used to create a mold. They all had some FOAM-iT 4 residue left on that I could not scrape off by hand. I followed all application instructions and exceeded the recommended wait time for product to work before testing. I used liberal amounts of product in each case.
I had enough items to clean that I could use each of the 5 products listed above at least once to attempt to clean the part. All the items were wood – most were 1/2″ plywood. After the test, I used soap and hot water to get all the product off of the cleaned pieces.
I used the following criteria when judging the results:
- The solvent must clean the FOAM-iT off the wood so it can be used again
- The cleaning effort should be as minimal as possible
- The number of reapplications of the cleaning solvent should be as low as possible
Other important factors:
- Low Cost
- Easy of application
- Avoidance of dangerous chemicals
Note: Unit costs may be reduced by buying in bulk.
Test Result Details
- Acetone – The biggest disappointment. After all the hype online, my expectations were mis-set. I wore the recommended gloves and eye protection (maybe a full HazMat suit next time?), and poured some of the product into a large, plastic bowl. I soaked a single board in the product for 20 minutes, checking every 5 on the progress and attempting to scrape the foam off with a knife. Eventually, it did come (mostly) clean, but only with significant effort. Also, a lot of the product was absorbed into the wood and I’m concerned now about using the wood again because of the adverse effects of the Acetone.
- Mineral Spirits – Not surprisingly, Mineral Spirits had zero effect on the dried FOAM-iT. I soaked a single board in the product for 20 minutes, checking every 5 on the progress and attempting to scrape foam off with a knife. I might as well have been using water – it was no help at all!
- Lift Off – The product lived up to the hype and did a great job of cleaning the FOAM-iT off of the wood with only a single application. This stuff sprays on, but has a gel consistency which helps to control where it works, which I think is a benefit. After 5 minutes, I was able to easily scrape off the foam with a screwdriver or knife. I felt safer using it than any of the other products tested based on the warnings on the label and the fact that it is a water-based and low VOC (Volatile Organic Compound = toxins). However, there was still warnings about ingestion, eye and skin contact, so it’s not totally safe.
- Goof Off – The product did a great job of cleaning the FOAM-iT off of the wood, but required 2 applications. Goof Off’s slogan on the bottle may be “Works the 1st Time”, but that was not the case for me, unfortunately. I bought it in a drip can which was a bit messy and required me to use my fingers to open/close the bottle (quite a challenging lid to open) despite the warnings about skin contact – it also comes in a spray bottle which would be better, but I wanted a small trial size since I wasn’t sure it would work. This was a more viscous product than the Lift Off and a lot of it was either absorbed into the wood or ran off. I think it it were more gel-like, it could have done the job in a single application. Because of the 2nd application, it did require a bit more effort to clean the wood.
- Goo Gone – This product had zero effect on the dried FOAM-iT. In it’s defense, it makes no claims about being able to clean expanding foam, so I was not surprised. It sprays on and has a gel-like consistency which helps to concentrate the cleaning. It has a nice citrus fragrance – that’s about the only nice thing I can say about it in this context. After 20 minutes, I gave up and used Lift-off to finish the job.
The clear winner for me is Lift Off. Despite it being the most expensive product, it best met all my primary requirements. In addition, I really like the fact that it is environmentally friendly and the least hazardous product I tested. Moving forward (now that I’ve confirmed it really works), I’ll buy in larger quantities in order to lower the unit price.
The foam lifted off easily after one application just using a screw driver to scrape.