Changing Contact Adhesives

Unfortunately I had a fair number of other things to do this weekend, so I didn’t get as much done as I really would have liked.

Typically for attaching N scale roadbed and track, I use DAP’s Weldwood contact adhesive. What can I say – it’s cheap and it works.  However, the stuff is a witch’s brew of organic solvents that – in addition to potential biological side effects – features prominent warnings about causing an explosion when being used, say, ten feet from a furnace.  During the summer that’s not an issue, since the furnace is shut down dead (and I have an electric water heater, so that’s not a concern).  Since it’s now winter, ventilating the basement adequately to avoid the “big boom” isn’t as much an option.  So I set out in search of a better adhesive that would be less likely to form a mushroom cloud in eastern Colorado Springs.

What I found was 3M’s Fastbond 30NF.  It’s still a polychloroprene contact cement, but the chemical engineering wizards at 3M have figured out how to make it primarily water-based, rather than all the organic solvents in most other contact cement.  It’s explicitly marketed for its nonflammability when wet.  In fact, the datasheet shows that it has no flash point – you literally can’t ignite it.  Sure, it’s also rather expensive ($100/gallon), but less so than blowing up your house.

The good news is that it works, and works very well in terms of bond strength.  The bad news is that “Fastbond” doesn’t live up to the fast part of its name.  It has a significantly longer wet stage than the organic solvent-based stuff, which is understandable even in such a dry environment as a Colorado winter.  I found that I usually had to wait about 20-30 minutes between application and actually being able to adhere pieces together.

The good news is that my concerns about it not bonding strongly enough (because, somehow, I assume anything not based on hideously harmful and/or flammable chemicals is inferior) were completely baseless.  The 30NF bond strength seems significantly stronger than the Weldwood, up and to the point that I had to put spacers down to keep the track from accidentally sticking when I was assembling the rail joiners.  At least twice I had a tie stick down so hard it detached from the rail when trying to get it up.  As long as it endures over time (and I have no reason to think it won’t), this stuff is superior from a bond aspect.

The other downside, besides working time, is that any frothy or clumpy spot will dry white.  However, most of that will be under ballast, and you just have to be more careful to only apply a thin layer to the bottom of the track.  Really it’s just about learning to apply more carefully than the “slather it on” method used in the past.

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