For amber malt, continue heating until the cut section is distinctly light buff, usually 45 to 50 minutes. If brown malt is needed, raise the temperature at this point to 175 C (350 F) and wait until the cut cross-section is a full buff, i.e. about the colour of the paler types of brown wrapping paper. When the correct colour has been reached, remove the tray from the oven, allow to cool and store the roast grain in an air-tight screw-top jar (large kilner jars are ideal). If used soon after production, the flavour imparted by home- roasted grain is superior to bought grain.
The roasting times given above are intended only as a guide to producing the wanted roast grain Practical tests on the oven available will enable home-brewers to adjust the time and temperature to produce the colour needed.
Crystal malt, which is usually available, has about the same colour potential as brown malt but a more caramel-like flavour.
Set the oven at 70-75 C (160-170 F) and put in the tray of grain (the grain bed can be a little deeper - up to 1.5 inches, say) and leave for 2 hours to dry out the grain. Raise the temperature to 88-94 C (190-200 F) for 30 mins then to 110-115 C (230-240 F) for a further 30 mins. Check the colour as above. If insufficient colour, then check at 15 min intervals. If after 1 hour at this temperature, colour has not been achieved, raise to 120-125 C (250-260 F) and continue to check at 15 min intervals. The resultant Pale Amber should be able to mash itself.
For Amber malt, after the grain has spent 1 hour at 110-115 C (230-240 F) raise the temperature to 127-132 C (260-270 F) and check colour every 15 mins.
*** And note: these diastatic darker grains will be more acidic than normal pale malt and if large proportions are used in a mash you might have to make an allowance in you water treatment.
I hope that helps. Good mashing.