The Guild’s workshops and firings are held throughout the year. The venue for the workshops is West Herts
College,Watford, and the wood fired kiln is located at Boxmoor. Kiln firings are organised during the summer and autumn months.
BOXMOOR WOOD FIRED KILN
For those of you interested in taking part in the wood firings in the future, please do take the time to read the articles below in preparation for the firings coming up.
- wood firing briefing details
- Glaze testing brief
- DCPG Glaze Tests
- Glazes cone 10 wood-firing (1)
- DCPG RiskAssessment Boxmoor 2018 (revised)
- accident form
BOXMOOR WOOD FIRING APRIL 2018 – details
27 July 2018
Boxmoor Kiln 28th April 2018 Firing Report
The full report includes documents –
Boxmoor Kiln Design Principles,
Boxmoor Firing 28 April 2018 Kiln Log,
Boxmoor Glaze Recipes 28 April 2018 Firing.
The programme was as follows –
April 21st AM – Put up gazebo, tables etc and start glazing pots for firing.
– Carry out works to the kiln as previously listed before being able to pack kiln.
PM – Continue glazing and start packing kiln
April 22nd AM -Continue Glazing and packing kiln
PM – Complete packing kiln and brick up
April 28th AM – Start to fire kiln
PM – Continue with firing
April 29th AM – Continue with firing
May 2nd – Strike and clear kiln, take down gazebo and clear away.
This programme was very successful. Once again I would like to thank those 14 or so members
who turned up over the two weekends, to glaze their pots and participate in firing the
Boxmoor Kiln. We counted 183 pots that made it into the kiln, and collected £70 for Guild
funds.
The two glazing days went superbly, helped no end by the glorious weather. The Guild
provided four glazes, a Shino, Celadon, Tenmoku and an Ash glaze, details as set out in the
Boxmoor Glaze Recipes 28 April Firing report. A number of other members glazes were
available
The last weekend, the weather not so good, but that did not appear to put anyone off. I hope
everyone had a good time, it seemed a very social occasion.
It’s a pity the Kiln Gods were not with us on the day.
This firing did not reach the required temperature of 1300deg C and consequently the glazes failed
to mature. Test rings of the four glazes detailed on the recipe sheet, pulled from the kiln at the end
of the firing, showed that they were all underfired. Therefore, we can’t say for certain that these
glazes work in this kiln at 1300deg C.
Previous firings have reached the correct temperature or at least in parts of the kiln, though I can’t
confirm whether this was 1300 or 1280. These are all now anecdotal reports, though the Ben
Brierley firing was reputedly the most successful. His firing did take a long time and did stall due
to wet wood. This could also be a feature of too short a chimney slowing the combustion of the
wood.
Paul Rowbotham remembers that Ben kept the top stoke sealing bricks in place during the firing,
which has the effect of drawing air through under the top fire bars, and across the hot embers,
adding to the efficiency of the burn. We had planned to make a stoke hole door for the same
purpose, but never completed it. During the firing we did utilise a broken kiln shelf to block the
stoke to achieve the same purpose, but as it was a lash up, it was clumsy and not easy to do.
However in the September 2017 firing, we had the stoke completely open and that fired OK to
1280deg C and fairly quickly. I personally think it very unlikely that this contributed in any major
way to the kiln stalling.
Possible Reasons for kiln stalling –
Ignoring those actions that may require major structural works to remedy
1. The current chimney is clearly too short, as set out in the Design Principles Report. This
leads to problems with the burn, and especially leads to choking when too much wood is fed into
the stoke.
Solution is the raise height of chimney. Better to try with a dis-mountable chimney section first
before building in brick. The Trust may not allow the chimney to be extended permanently anyway.
2. Wood not good quality. We used almost entirely garden prunings and pallet wood, both of
uncertain parentage. This is not very good wood. For the Sept 2017 firing we had the benefit of
some kiln dried, pine offcuts from college projects, though small, it burned really well. Pine and
soft coniferous woods give a greater calorific value than hard woods. See the Olsen Kiln Book page
195 and Ian Godfrey”Kiln Building” page 14. Also they burn quicker as they are less dense.
Solution is to try to find convenient source of better timber. Pallet wood is cheap though, and if the
extra chimney height works with pallet wood, then problem goes away.
3. Wood too big. The thinner the wood the easier it is too burn and the quicker. We did
increase the amount of chopping we did at the end of the firing to see if we could overcome the stall
but to no avail. Problem is that it requires quite some physicality to chop wood for the length of the
firing, and is very tiring. As the Guild members are generally mature individuals, this is quite some
ask. There is still a tendency to over-stoke as well, “to get the big yellow flames”, a real problem
when the wood size is quite big.
Solution. This will probably make the most cost effective difference, in combination with the taller
chimney. If we continue to use pallet wood for cheapness, then we need to get it cut down using a
saw bench or similar, that is not as physical as chopping wood. Pallet wood does not chop straight
anyway. Otherwise we could pay more for better quality wood of the right size, but this could be
expensive.
For the Sept 2017 firing there was a Working Party on a Wednesday morning where members were
asked to help “chop logs”. I don’t know how successful that was, but for the next firing we would
be advised to consider a weekend or a long enough period to ensure all the wood was of an
appropriate size.
4. Use a forced air system. For my small garden kiln, I used a hoover as a blower to raise the
temperature as I was sticking at the same cone 5. It may be that for the next firing we have a couple
of fans on standby, that we can bring into play if we get the kiln stalling again.
5. Fire to a lower temperature. If all else fails, this is also a solution, but you will lose the high
fired wood effects on the pots.
The other feature of this and earlier firings is the difference in temperature between different areas
of the kiln. It is clear from the Kiln Log Report that the floor of the kiln near the door, is hotter than
the top/rest of the kiln. Also, we still have the problem as in earlier firings that the door end fires
hotter than the chimney end. It is probable that we won’t solve this until we can get the kiln to
temperature easily and be able to properly soak the kiln. We know what to do with the split
dampers to help control the temperature at each end of the kiln, but the difference in temperature
top to bottom may just be a feature of the high kiln chamber.
Part of the work we carried out on the 21st April, was that we opened up the spy holes into the kiln,
and we are now able to see cone clusters top and bottom both ends of the kiln easily, so enabling
better control. Also for this firing, we had cones in the central stack and we kept a record of all
these cones, as given in the illustrations to the Kiln Log Report. We need to do the same for the
next firings.
The additional kiln props we ordered from Bluematchbox proved adequate and we did not need, and
hopefully will no longer need, to borrow from others.
The scrap drainage grating that we fitted as a fire grate both sides of the kiln, worked well and
allowed small wood pieces to be burnt at the lower level, as well as the larger pieces that fitted on
the upper fire bars.
Jerry
Grangrad71
The Box Moor Trust
London Rd, Hemel Hempstead, HP1 2RE
https://goo.gl/maps/6dn6XYwGJBB2
Addendum – I have a 3 metre tall metal kiln chimney, the same cross section as the Boxmoor
Kiln. This was originally from Pauline Ashley’s kiln, and I used it on my gas kiln that I blew up.
I am prohibited from re-building a gas kiln, so this chimney would be available to the Guild,
should the Committee wish it.
16 April 2018
18 March 2018
26 February 2018
Please put the following dates in your diary.
The next work party weekend will be March 17th and 18th, when we are planning to cover the kiln with an kkadobe layer, please let me know if you can assist in this, either one or both days.
The glazing weekend will be on the 21st and 22nd April. Please bring your bisqued pots to be glazed and packed in the kiln over this weekend. The Guild will provide a number of glazes as before, one of which we hope will be an ash glaze. Those who were on the Ash glazing course, perhaps you have developed a personal ash glaze that you could share with the other members? There will be a flat charge of £5 for the firing, so the more pots you make the better.
The kiln will be fired on the following weekend, starting on the 28th and over night into the 29th April, if necessary. This firing will only be possible if we have enough pots to fill the kiln. Please consider refiring items that did not quite reach the correct temperature in earlier firings, and indicate if any of the pots you intend to fire, are refires.
Can those members who intend to include pieces of their work in this firing, please register your interest with me. Please indicate if you wish to be included on the firing rota (this is likely to be overnight, so also indicate if you are OK to be there at night). Also, provisionally, the number of pots you are aiming to have. We will need have these details finalised before the glazing weekend. Also, please indicate if you would be able to come one evening in the following week to collect your pots, rather than the next weekend, which is the May holiday weekend
Jerry Seaborn
07766305431 (text or Whatsapp)
JJSeaborn@outlook.com
Woodfiring at Boxmoor, September 2017
Soda firing at Northfields, Tring, August 2016
