On 04/10/17 19:23, john.west wrote:
In trying to deal a death blow to Japanese Knotweed in the garden, i
have bought an old paraffin blow torch.
The leather washer of the pump is very dried out and no longer a good seal.
To moisten it, to expand the piston leather; am i better using paraffin
or dubbin or would it be kinder to the leather to use a vegetable oil
like walnut oil? Thanks.

You are wasting your time and money, as Japanese Knotweed roots can
penetrate metres underground. You can burn the topgrowth down to the
ground with a blowtorch, but it will resprout in spring. The best way to
deal with it is repeated application of glyphosate (Roundup), and even
then it will take years to get rid of it completely.

There are legal issues surrounding disposal of Japanese Knotweed. See he
https://www.gov.uk/guidance/prevent-japanese-knotweed-from-spreading

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Jeff