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perkolator

Member Since 08 Feb 2012
Offline Last Active Dec 02 2016 03:39 PM
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Posts I've Made

In Topic: Technical Requirements Skutt Kiln

02 December 2016 - 02:54 PM

I just went through this with our 714 -- it takes a 20A dedicated circuit.  

 

Was having issues with out smaller 609 (turned out to be a bad receptacle) and had an electrician in studio to inspect power on both our 120v test kilns.  I was questioning the 20A circuit for the 709 since its amperage rating is too close and if we managed to fry a less amp kiln's wiring, what about the one drawing more juice.  Both Skutt and the electrician confirmed 20A was the common setup on both models since a 25A circuit is only possible at the breaker side, there are no 25A receptacles and the kiln would have to be hard-wired to a shutoff for this to work.  I need to be able to unplug the kiln for stuff like element and brick repairs after someone blows up their test tiles in these powerful little kilns - so I chose to just switch to dedicated 20A twist-loc receptacles and plugs for ease of service.  The other way suggested by the electrician was to possibly setup the kiln with 30A and install a lower amperage inline fuse on the control box.


In Topic: Silicone Caulking Cure Time?

02 December 2016 - 01:43 PM

Silicone generally takes around 24hrs to cure.  It cures with humidity in the air, so I suppose if it's in a humid environment, possibly with heat and airflow it will cure faster.

 

I like E-6000, it generally takes 24hrs, but sometimes takes longer.  These I'd go 72hrs if you had the time available.

 

I usually prefer a 2-part epoxy though.  Not too much a fan of the quicker 5min stuff, the longer the cure and the more opaque, the stronger it is.  If it doesn't have to be a clear, PC-11 (white) and PC-7 (charcoal) are my preferred "strong" paste epoxy.  I believe the PC epoxy is stronger than JB weld, but JB beats it in thermal resistance.  I can only find it on the shelf of Ace Hardware; or online.  Don't really have a preferred clear 2-part epoxy yet, but I'd go 30-min cure.


In Topic: What Happens When A Relay Fails?

21 November 2016 - 01:18 PM

Late to the party and I didn't read everything in the entirety :) but it sounds like in order to satisfy some concerns from higher up, you need better shutoffs in case of emergency.

 

In a setting with multiple users, the kiln should be wired to a shutoff/disconnect box like pictured above, from there it gets power from the main panel.  This way the technician/staff can lock out the electrical panel for whatever reason and everything will be completely dead.  When they want to give access, they tun on the breaker and leave the shutoff/disconnect box to kill power in case of emergency, the user will notify the staff of emergency shutoff so they can lock/tag out the equipment.

 

I've had relays fail in both directions, but I never really saw any bad problems from a relay getting stuck closed (powered on).  In those instances (WAY fewer than relay stuck open/off) the kiln just held temp longer as it tried to cool down.  You kinda notice when your control box says complete, yet you still hear power going through the box.  My kilns are plug-in, so I just pull the plug or flip the breaker.

 

 

 

On the gas kiln, you can get a large main gas solenoid or manual lockout valve that can be used to lockout the gas supply upstream.  Since kiln most likely has electronic components, you can also simply have an electrical shutout to keep non-authorized users from tinkering - can't really start up the kiln without power.  I never rely on the gas solenoids when shutting down my kilns, I ALWAYS close the burner and pilot valves manually afterward.

 

I like the idea of an external timer on the gas solenoid - but in this setting being at a school they may want an actual lockout device.


In Topic: Silica Sand For Use Under Slabs

02 November 2016 - 12:33 PM

12"x12" isn't that big of a slab.  dunno what firing schedule you're using but likely it's too fast.

 

slabs and similar work with large flat surface areas against a shelf (like slabs, and big platters/pots without a foot trimmed into it) tend to have two main issues with firing.

 

-One is that they are a big surface area, sitting flat against a shelf, thus the heat cannot easily penetrate to the bottom, center, of the clay.  Because it was cooler than everywhere else during the time you were candling your kiln, by the time you go to your next stage of firing, this cool section kinda rapidly heats up and thus you get blow-outs. Raising/elevating the piece will help tremendously. Also slow down your firing to compensate for lack of heat penetration.  Kinda the same concept if you were to stack a really tight, low height shelf in the bottom of your kiln - the heat can't penetrate very well.

 

-Second issue is more likely with larger work than the scale we're talking about, and the problem is usually cracking due to the friction and drag caused by the physical weight of the mass as it's trying to expand/contract in the kiln.  Something under the piece

 

 

Yes, silica sand can work if you need to sit it flat.  Grog will also do the same thing.  Putting a layer under your piece will act as ball bearings and facilitate the movement as the clay expands/contracts.  Since it's not a solid, it will also allow moisture and heat to pass through the interstices and make its way to/from the bottom.  Another alternative is raising the piece on pieces of broken kiln shelf or clay pucks.  Most of the time with big work, I use either the broken shelf bits or balls of kiln wadding (1/3 each: grog, silica, clay) - they do the same thing, but they have one main factor that makes me go toward them before loose sand/grog......Grog/sand can fall through the shelf crack/joint to the work below, the wadding stays put.  Another benefit to the wadding and sand is that they will self-level out which is great if your kiln shelves aren't perfectly flat, but your piece was built on a flat surface.

 

Yes, slabs fired at an angle on their side can definitely warp.  Depends on how thick/thin, how heavy, how big, the temp you're firing to, etc etc.

 

I lean stuff on soft brick all the time as long as there's no glaze.


In Topic: Change In Kiln Sitter Fireing

02 November 2016 - 11:56 AM

I would also replace the rod tube assembly as a whole unit vs just the rod, I want to say they run around $50 or less.  Then re-adjust your plunger latch settings with the tool and test fire the kiln.  Also, are you consistent with bar placement in the sitter every firing? If it's consistently doing this, you may need to set your plunger catch tab so it gets where you need it.