Hi Tim and All, As Clinker basically is a crust which forms over the fire on our size fireholes I think that is would be almost impossible to see it and if you could see it even more impossible to get it out. On full size land based boilers the technique was to use tools to break the clinker up,then rake the broken bits towards the firedoor and allow them to cool.After it had cooled down the bits were then raked out of the of the firebox usually onto the boilerhouse floor.Better stokers had a steel box which fitted on the front of the boiler, level with the bottom of the firedoor into which the clinker was dropped. All a bit impossible with our size boilers and I think that the best you could do is break it up, push it to one end of the firebox and hope that you can get enough fire with the remaining space. The alternative is to use only Anthracite or Anthracite mixed with Coal. Regards Clif > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line. MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.