The simplest and best way to harden conkers is to put them away in a drawer until the following year.
However, if they were not attached to a string when new and soft they will have to be drilled.
Many children and grandchildren have played with leftover conkers, some of which were 50 years old.
They have never been defeated.
We have been in conker fights for about 50 years and we always soak them in vinegar.
This hardens them into champion conkers. I was content with this method until a few years ago when I was beaten by someone who had smeared his conker in Oil of Olay. Apparently, this made the conker more malleable, allowing it to absorb the impact of my prize pickled nut.
Neither baking nor pickling in vinegar is an effective way to strengthen conkers. Baking makes chestnuts brittle, which means they can be knocked off their string with a single blow. Pickling rots the inside. Varnishing, another technique used, is also ineffective, and readily detectable.
In fact, no intervention is necessary to toughen a conker.
Simply avoid using chestnuts from the current season, conkers is obviously an autumn pursuit, and use old ones instead. The older they are, the harder they are. Such conkers are readily identified, instead of having a glossy chestnut brown skin they will look dull and dark, perhaps even black.
And finally, make the hole for threading the string as narrow as possible.
The best way to make a conker invincible is either to leave it for a year and use it in the season after you found it or, to speed up the process, bake it. Put all your conkers in the oven at 120 °C for about two hours.
Do not leave them any longer otherwise the flesh inside the conker will become charred and weak. Even if the heat breaks the shell of your conker, the flesh will be rock hard.
Do not put your conkers in vinegar. Although vinegar hardens the shells, the flesh will soften up if there is any gap in the shell, making the conker useless.
Some folks have been disqualified from school conker championships for having a conker that was vacuum-impregnated with epoxy resin.
Every conkerer disagrees with every other on how best to produce an invincible nut. As such disputes are an essential part of the sport, we leave the question with the totally contradictory answers given above.
What do the British really do with chestnuts attached to a string? We suspect it doesn’t involve consumption.
