Peter Pugger VPM 9 cap leaves green particles

[Marge]

I've been using my new Peter Pugger  VPM 9 for a few months now. The clay that first extrudes from my pug mill always has green particles on it.  It's obviously left from the cap when I take it off of the clay as it extrudes. I have contacted the company who said it may be a reaction from the clay I'm using as it comes into contact with the cap and to stick that clay back in the pug mill. The clay with any green on it does not burn off but stays green on my pots. It's almost solid pieces of green that I can pull off of the clay.  Has anyone had this issue, or have any advice? Thanks!! --- Margie

[Mark C.]

funny you mention this as my VPM 30 CAP LEAVES A BLUE COLOR in center of pug where it touches the rubber cap. This is withn cone 10 porcelain and always burns away in bisque and is never seen again. I fire to cone 11 in reduction. You did not mention what clay  you are using or temps you fire to?

Its an oxidation thing I feel and cuases me no worries.-Afew photos of this gren on fired wares may help us.

[Marge]

I use white stoneware and fire to cone 6.  I've thrown away my finished pieces where the green shows through my glossy white.  I will finish a piece with the green flecks on it and try with a different glaze. It's just strange that the pieces feel hard and can be peeled off of the clay that is pugged. Thanks!

[Min]

Very odd that the green doesn't fire out. Plastic clay bag held on with with a piece of elastic instead of the cap or just lining the cap with a bit of plastic to make a barrier between the cap material and the clay should fix it.

[Mark C.]

48 minutes ago, Min said:

Very odd that the green doesn't fire out. Plastic clay bag held on with with a piece of elastic instead of the cap or just lining the cap with a bit of plastic to make a barrier between the cap material and the clay should fix it.

GREAT IDEA

[Marge]

Min I will try this today!! Thanks so much for helping!--- Margie

 

[Magnolia Mud Research]

Or you could make a ceramic cap to cover the end of the extruder.  

My speculation is that the cap is galvanized -- which means the cap is coated with Zink; back in the 'good old days,' Zinc chunks were thrown into the kiln to make green bricks.  

LT
 

[Mark C.]

3 hours ago, Magnolia Mud Research said:

Or you could make a ceramic cap to cover the end of the extruder.  

My speculation is that the cap is galvanized -- which means the cap is coated with Zink; back in the 'good old days,' Zinc chunks were thrown into the kiln to make green bricks.  

LT
 

The caps are  black rubber which is starnge as they leave a color behind in center of pug

[Dick White]

What Mark C. said. The caps are black rubber, and form an integral part of sealing the chamber when vacuum de-airing the clay before pugging it out. It has been my experience with both our  Peter Puggers that if the inside of the rubber cap is not kept clean, it will not properly seal and a vacuum cannot be achieved. Thus, regarding an earlier suggestion of putting a piece of plastic over the end of the barrel before putting the rubber cap on over it, that may or may not produce an adequate seal for the vacuum process. Try it, YMMV. And yes, both our PPs leave a blue-green-grey stain in the center of the exposed end of the last pug left in the barrel when the machine is empty. In my experience with both dark and white stoneware, the stain does not affect any of the fired wares. Again, YMMV.

[Mark C.]

(In my experience with both dark and white stoneware, the stain does not affect any of the fired wares. ) yup it burns off clean for me as well.

[fergusonjeff]

I get the same blue color from white clays in my PP.  I asked the company and they said it is just a harmless reaction of clays with the dyes in the cap.  I burns off with no issues.  Something green that sticks around through the firing is something all together different that I have not seen.

 

[CactusPots]

Now here's something I never thought of.  You put the cap on to achieve vacuum?  I find the clay in the barrel seals the mixing chamber completely.  In fact, if I run up the vacuum and leave it for half hour, the vacuum is maintained.  I thought the only purpose of the cap is to keep the end of the clay from drying out.  Never cleaned it either.

[fergusonjeff]

CactusPots.  I think you might be a little confused.  With the peter puggers, the initial vacuum pull usually seals the back vacuum chamber, but not the mixing chamber.  I usually have to start pugging for a few seconds before the seal between the mixing and vacuum chambers is broken.  then turn back to mixing as the mixing chamber vacuums down.  If the cap is not on while the mixing chamber is under vacuum it will not seal.  I tend to overfill the chamber so as soon as you turn on the vacuum it pulls a little clay through the gap between the chambers and seals off the vacuum chamber.  Starting pugging pushes clay the other direction and breaks the seal, usually in 10-15 seconds.  Does this make sense?

 

[CactusPots]

Not really.  I understand the vacuum chamber is not the mixing chamber.  So, here's the question then.  If the vacuum gauge reads the vacuum chamber and not the mixing chamber and they aren't the same, how do you know that you have a vacuum in the mixing chamber?  I say, by the clay that is pulled into the vacuum chamber and no air in the clay.

6 hours ago, fergusonjeff said:

If the cap is not on while the mixing chamber is under vacuum it will not seal

Here's the thing.  My clay appears to me to be fully de aired.  I don't wedge out bubbles, generally.  I run up the vacuum while the mixing is on.  The vacuum stays up while mixing.  No cap.   At all times the clay in the nozzle provides a better seal to the vacuum than the cap.   What am I missing?   Or do we not disagree?

[neilestrick]

3 hours ago, CactusPots said:

Not really.  I understand the vacuum chamber is not the mixing chamber.  So, here's the question then.  If the vacuum gauge reads the vacuum chamber and not the mixing chamber and they aren't the same, how do you know that you have a vacuum in the mixing chamber?  I say, by the clay that is pulled into the vacuum chamber and no air in the clay.

Here's the thing.  My clay appears to me to be fully de aired.  I don't wedge out bubbles, generally.  I run up the vacuum while the mixing is on.  The vacuum stays up while mixing.  No cap.   At all times the clay in the nozzle provides a better seal to the vacuum than the cap.   What am I missing?   Or do we not disagree?

In a Peter Pugger, there is only one chamber. It's not the same as a pug mill, which has a chamber in the middle between the intake and the extruder specifically for the vacuum. https://peterpugger.com/history/how-peter-pugger-works/

[Bill Kielb]

4 hours ago, CactusPots said:

Not really.  I understand the vacuum chamber is not the mixing chamber.  So, here's the question then.  If the vacuum gauge reads the vacuum chamber and not the mixing chamber and they aren't the same, how do you know that you have a vacuum in the mixing chamber?  I say, by the clay that is pulled into the vacuum chamber and no air in the clay.

Here's the thing.  My clay appears to me to be fully de aired.  I don't wedge out bubbles, generally.  I run up the vacuum while the mixing is on.  The vacuum stays up while mixing.  No cap.   At all times the clay in the nozzle provides a better seal to the vacuum than the cap.   What am I missing?   Or do we not disagree?

In the end it’s all about what vacuum can you achieve over as much clay as possible and for how long .  So long  as you can achieve enough to suitably deaerate, it doesn’t matter how you seal it. It would be helpful to quantify this though as it would be a good measure of pump performance. What does the gauge say you can maintain?

[liambesaw]

Why would you need to deair while you're mixing? It's still going to pass through a vacuum while it's being augered, and still compressed as it's pushed out.  Seems like deairing while mixing would be redundant

[Bill Kielb]

33 minutes ago, liambesaw said:

Why would you need to deair while you're mixing? It's still going to pass through a vacuum while it's being augered, and still compressed as it's pushed out.  Seems like deairing while mixing would be redundant

Must require some vacuum else manufactures likely would not add a pump, right? Must not be too much, at 28” hg, water boils at 90F.  Could double as a freeze dryer at some point. LOL 

[liambesaw]

30 minutes ago, Bill Kielb said:

Must require some vacuum else manufactures likely would not add a pump, right? Must not be too much, at 28” hg, water boils at 90F.  Could double as a freeze dryer at some point. LOL 

Yeah but the vacuum pump is on the vacuum chamber, why does it need to deair the mixer too? If the clay is being mixed it's going to get air in it regardless of a vacuum being pulled on it

[CactusPots]

The vacuum gauge has an outside scale of 0 to 100, I get about 60.  The inside scale is 0 to 30, about 16.  I run the vacuum up while the pug mill is in mixing mode until I get that reading, then turn it off.  It stays in vacuum until it's being pugged out, at which time it loses the vacuum.  I've never tried to run the vacuum pump while it's being pugged.  I've never had anyone teach me how to use the tool, I just figure it out as I go.  I did appreciate Mark's advice on how to use the pugmill to soften clay.  Works fine.  Otherwise, the finished product is great and very usable right out of the machine and even better aged.

[fergusonjeff]

In a hurry this morning, but I am pretty sure this is the video that shows how to break the seal between the vacuum chamber and the mixing chamber.  Not sure if just pasting the url will work.

 

[Mark C.]

I run the vacuum while mixing or pugging -Thats the way the instructions say to do it. The idea is get the air bubbles out of clay and keep them out with either function. Its no big deal to run a vacumme in this machine so run it in all functions.

 

[Bill Kielb]

On 10/10/2019 at 10:13 AM, Mark C. said:

I run the vacuum while mixing or pugging -Thats the way the instructions say to do it. The ikdea is get the air bubbles out of clay and keep them out with either function. Its no big deal to run a vacumme in this machine so run it in all functions.

 

Makes sense, lower the pressure above the clay only helps remove entrained air. Must work, race proven. In the video it appears to stay in a slight vacuum right up until he opens the hopper to refill. Appears the outer dial is inches and inner is bar. His machine appears to achieve approximately 27" - 28" which is quite significant actually.