Wednesday, 28 December 2016

Making Your Own Schedules

Starting out with your own schedules is a bit frightening as you don’t yet know the capabilities of your kiln and the problems that might occur. This note attempts to give you some pointers on how to go about making your own schedules.

Start with the glass manufacturer’s recommendations.  Picking something from the internet or a discussion list may seem easy, but you cannot assess the quality of the posted schedules.  Many odd practices have crept into the kiln forming community. The manufacturers know their glass, so you should start there. They are the quality control standards for kiln forming.  Modifications will of course be required for your particular practice as it develops.

Enter the manufacturer’s schedule for the project you are working on and then watch while firing.  Watching does not mean staring into the kiln.  This would damage your sight after a while. This watching consists of quick peeks into the kiln to see what is happening.  These peeks will be at above 580C.  It is only then that there is enough light in the kiln to see what is happening.  At first the peeks will be at possibly only 30 minute intervals.  But as you near the target temperature, you will need to peek at possibly 5 minute intervals. The progress of the glass forming will be much quicker, so to know when the right temperature has been achieved, frequent peeks will be needed.

This observation will let you know if the glass is achieving what you want. If it is not, you can change the schedule while firing.  E.g., advancing to the next step in the schedule, extending the soak time, changing the working temperature to a higher point.  Be sure to read your controller manual to ensure you know how to do these changes during the firing.

If you have achieved the look you want before the target temperature has been achieved, advance the schedule to the next segment or ramp.  Record this temperature, as the next time you fire this set up you will want to be 5°C -10°C lower than this time.  You are aiming to achieve your look with a 10 minute soak.  So, depending on temperature, rate of advance and your kin, this lower temperature with a 10 minute soak should achieve your desired look.  Record this schedule. You will need to observe the next firing just to be sure the temperature and time combination you choose works. 

If the desired look has not been achieved by your top temperature and soak, you can raise the temperature 5°C -10°C, even if you have to interrupt the firing to change the temperature.  The controller will recognise which ramp is required to complete the ramp to the new top temperature without going through all the segments of the schedule.  Even if it does not, you can advance to the ramp you need.  The effect of these changes will be minimal in relation to the full and uninterrupted schedule and can be relied upon to work well on future firings.  Record the new schedule for future use.

An alternative to the change of the top temperature, is to extend the soak when the temperature has not achieved the effect.  You will need to keep peeking until the sought for profile is achieved.  Record this new soak time and the results for future firings.

As you can see it is important to record schedules, layup and results every time you fire.  This enables you to compare results and learn.  A log provides a good reference when you want to reproduce something that was successful.  It also records what did not go well and can remind you of what to avoid.

This process of observation, amendment on the fly, and recording actions and results helps you to get to your ideal schedule much quicker than by putting a schedule in and coming back the next day to see what has happened.