We have analysed optical spectra of two of the hydrogen-deficient knots ( J1 & J3 ) in the born-again planetary nebula Abell 30 , together with UV spectra of knots J3 & J4 .
We determine electron temperatures in the knots based on several diagnostics .
The [ O iii ] nebular-to-auroral transition ratio yields temperatures of the order of 17 000 K. The weak temperature dependence of the ratios of helium lines \lambda 4471 , \lambda 5876 and \lambda 6678 is used to derive a temperature of 8850 K for knot J3 and 4600 K for knot J1 .
Ratios of O ii recombination lines , which directly measure the temperature in the coldest regions of the knots , are used to derive temperatures of 2500 K for knot J3 , and just 500 K for knot J1 .

We calculate abundances both from collisionally excited lines and from the well-observed recombination spectra of C , N , O and Ne ions .
The forbidden line abundances agree well with previous determinations , but the recombination line abundances are several hundred times higher .
These results confirm the scenario proposed by Harrington and Feibelman ( 1984 ) in which the knots contain a cold core highly enriched in heavy elements .
Forbidden lines are almost entirely emitted by the hot outer part of the knot , while recombination lines are emitted predominantly from the cold core .
The C/O ratios we derive imply that the knots are oxygen-rich , contrary to theoretical predictions for born-again nebulae ( Iben et al 1983 ) .