There are two major issues of Health and Safety that currently arise with this project;
- Ping-pong balls are made out of Celluloid. Which is primarily composed of Nitro-cellulose, which is highly inflammable. They do also contain material to reduce this inflammability but I think any installation, at least in doors, would need to take extra precautions. My current approach is to investigate fire-retardant paints - intumescent and the like. I have links to UK suppliers but I haven't followed this up yet.
- Currently, by far the best glue for joining two ping-pong balls is Super glue. Of itself I don't think that this is too much of a problem, in the right hands. BUT it does seriously restrict public involvement in the construction. Super glue is quite expensive, for the project I estimate about 1000 pounds worth (at retail prices), so less than 10% of the capital cost but significant. But we couldn't afford to let kids lose squirting the stuff all over the place! Also I worry about them sticking themselves together.
I have tried other everyday glues but with no success. I think the source of the problem is that most glues work by absorption into the material of both the glue and the solvent. Celluloid, the material of ping-pong balls, is very non absorbent. So, they don't stick very well and take a long time to go off. Super glue goes off in under 5 seconds and, from my own tests, has a bond strength on a par with the strength of the celluloid - about 1 in 10 fail by tearing the celluloid rather than breaking the bond.
So, what alternatives do we have?
I'd love to find a product which has the sphericity, strength an weight of ping-pong balls which wasn't so inflammable and hard to glue, but haven't yet. If anyone could come up with an idea Id love to hear.
I think that these are problems to be solved rather than insurmountable obstacles! See
Construction Hirearchy for further discussion of this issue...