View Full Version : How the Bird Swing Happens.

RED Matthews
03-02-2011, 11:42 PM
Hello you FORUM people. I just finished this dissertation to tell a man how the bird-swing happens in the ABM production of Blow and Blow process bottles. I decided to post it here for your reading, and understanding. If you have questions, you will just have to get back to me with them.

This bottle was made on an ABM (Automatic Bottle Machine) and it was more than likely made on an Emhart IS Machine. ( IS standing for Individual Section).

In this process this bottle would be made upside down in the first stage of manufacturing. The gob of glass is dropped from the orifice ring shear off - into a delivery shoot system that takes it to the blank mold (the parison shaping mold) on the back side of the glass machine. The blank mold is in a closed position and it was closed around a part called the neckring that is operated and carried in an inverting arm system.

That neckring has a guide ring inside of the assembly that is responsible for shaping the top sealing round surface of the finish. Inside that assembly sets a Blow and Blow plunger in the up position.

When the hot gob of glass is dropped it goes through a funnel (a piece of mold equipment) and into the top end of the parison mold cavity. After the dropped gob is in the blank mold, the funnel arm carries it back away from the action and another arm swings in placing a baffle in the recessed top of the parison mold. Air is blown into the parison mold cavity which pushes the molten glass down into the neck area of the potential bottle parison and forms the bottle finish.

Then the little plunger is pulled back down leaving a little cavity in that end of the gob. Then air pressure blows the hot glass up into the little cavity creating a hollow bottle form that is called the parison.

The distribution of the glass thickness in the Final Blow Mold is determined by the shape of this blank mold cavity.

After that has happened - the blank mold opens and the arm with the glass still in the neckring is carried up and over to the Final Blow Mold side of the machine where it is waiting open for the parisons' delivery.

At this point the Final Blow Mold arms close the mold around the parison and an arm carrying the blowhead, comes over the finish end; which sticks up out of the mold, and delivers a blast of air into the parison blowing the parison glass out to the mold cavity and down to the bottom plate.

After that the mold opens and a take-out jaw lifts the bottle out and onto a dead plate near the hot end conveyor. From there a push-out arm sweeps the finished bottle out on the hot end belt

Now then - in that inverting motion of the parison form throwing the hot glass up and over to the final mold position. If the glass is a little too hot in temperature, the inverting motion can cause the inside walls of that parison to touch each others inside walls. Then when the final blow occurs the contacted glass will stretch and pull a birds-swing across the bottles cavity. So that is how they are created.

Inspection equipment normally catches them before they get to the product packaging system on the finished bottle end of the annealing lehr.

I just decided that a lot of people collecting bottles might not know how this anomaly happens.
RED Matthews

03-03-2011, 12:12 AM
Thanks RED...I actually understood that. Interesting info.

03-03-2011, 12:18 AM
Hi Red,very facsinating and a well desrcribed explanation for all of us.Thanks for taking the time to post this information.I guess a bird swing is nearly impossible to malform in a blow pipe scenario or can it actually happen that way also.I hope all is well with you and Agnes. Take care Steve.

03-03-2011, 04:26 AM
Very informative Red. I have a question. Why is this mold seam line going down the face side of this bottle? Usually you see the seam on the flat side or corners.


03-03-2011, 04:27 AM


03-03-2011, 04:30 AM


RED Matthews
03-03-2011, 07:25 PM
Well rockbot; I doubt that is a mold seam but I am sure one would have to see that in hand. We had a strange line on a square bottle a while ago. This one looks like it isn't straight enough to be a mold seam. How far does it go up the neck? Was the finish tooled to take the mark away? Is there any indication of a mold seam on the corners that comes up to the neck.of the bottle. What about on the bottom does it look normal? Thanks for showing it to us. If you want to mail it to me I will study it some and send it back. All we would be out is the postage - I'd pay the return. I have done this with a lot of the odd anomalies that are showing on glass. RED Matthews.

03-03-2011, 08:15 PM
Hi Red, I inspected the bottle closer and the mold seam is on opposing corners. It ends at the top of the shoulder and neck junction. The bottle looks machined because the unidentified seam goes up to the top. The unidentified seam also connects to the oval base seam on both sides of the bottle.
I have a few more pictures.


03-03-2011, 08:17 PM
base with unidentified sea.


03-03-2011, 08:19 PM
base. looks like a three digit # inside a diamond. IPG?


03-03-2011, 08:21 PM
corner seam line ending at shoulder.


RED Matthews
03-03-2011, 11:14 PM
Hi, I thought I was writing a reply to you regarding the picture of the bottom of the bottle. All of a sudden it went away to somewhere. I must have pushed the wrong button. I was questioning this picture because it looks like there was a distribution of glass problem in that area. Is the glass on the upper side thick? The two upper corners of the glass looks different than the bottom corners. Of course it could just be the lighting.

Just curious.Thanks RED Matthews

03-04-2011, 01:12 AM
The partition was probably closed in the mold and then spun around before it was blown leaving the mold
Lines in the glass before it was blown out...

03-04-2011, 01:21 AM
For the record bird swings can happen in any blown bottle, hand or machine made. As the glass was blown instead Of one solid bubble of air in the glass the glass Pulled apart in one place and stretched out. Usually this stretch of glass broke and swung down and attached itself back to the same side of the bottle, making a little loop. Or it could of stayed intact making the classic, and rare bird swing. It's also possible that instead of just uneven distribution of air in the gather the gaffer could
Of inhaled on the the blow pipe sucking the gather back together so it stuck back to itself creating the bird swing when it was reblown out. Of course if the air made It back out the pipe it would of burned the gaffers lungs something mighty!

The only inconsistency if found with this is that you will not see evidence on the opposite side of the bottle from the bird swing...

03-04-2011, 03:26 AM
ORIGINAL: tigue710

The partition was probably closed in the mold and then spun around before it was blown leaving the mold
Lines in the glass before it was blown out...

Would that have been done by accident? Why does it continue up the neck and onto the lip?


03-04-2011, 12:33 PM
Yeah, it would have been accidental, could of been a malfunction with the machine, etc... This is only conjecture of course, but a more likely reason for the seam lines to be in the glass like that. The bottle would not have been able to be removed from the mold if it was blown that way, unless it was some strange 4 piece mold. Another thought is that some of the early machines dropped the gather from the part of the mold that formed the lip into the the part that formed the body, (these mds always have a seam line going up the neck to the lip, then around under the lip halfway, then over lip), and whe the gather was being inject through the lipping mold it picked up and carried the seam line through the gather into the bottle mold, leaving the seam in the glass as it stretched.