Eric42

Possibly Acute Oak Decline (AOD) There is a good description of the symptoms here

Always thought that nice blue colour came from all the embedded barbed wire and staples in hedgerow firewood 🙂

We have a Clearview Vision 500 that only every burns wood, so except for the annual chimney clean it always has a good bed of ash over the grid. No problem with air control, when the spin wheel is closed the primary air is completely shut off. Occasionally I poke a hole through the ash layer and use bottom air to get it going quickly, however most of the time I light the fire "top down", which is recommended nowadays to minimise start-up emissions (and is always fascinating to watch !)

If you have the time, Hawthorn from hedges that have never been flailed and have almost no thorns. One of the most satisfying things in life is to see a hedgerow regenerated by coppicing/laying a few years ago, then go home and watch flames from seasoned logs cut from that same hedge.