Click here for Glassblowing School/Class/Studio/Artist Geographical Search with 32 Criteria!

Round Pipe Glassblowing Mold

I was considering purchasing "Glass Masters at Work: Mark Matthews" (by Corning Museum of Glass CMOG), a film by Robin Lehman
which is available from the CMOG GlassMarket here or directly from Mark Matthews Glass here.
But I also found Glass Masters at Work: Mark Matthews (by Corning Museum of Glass CMOG)
as a short video on YouTube by where Mark Matthews demonstrates creating a 7-lobe Rainbow marble,
which he describes as 28 canes, 14 in each rainbow, each color is a transparent overlay.
The colors are tuned very carefully so their intensity is very similar.
In the YouTube video, at 1:14 (one minute fourteen seconds) in, you see Mark Matthews ram his gather into this mold.
He describes that this must be done carefully, as the broad faces of the mold can push the colors around.
mark matthews - glassblowing mold based on 7 pieces of round pipe
From that round pipe mold and the gather of canes, Mark Matthews was able to make these large marbles, as shown on Brian Bowden's website.
Mark Matthews new lobe rainbow marble from pbase bkbowden front view
(front view)
Mark Matthews new lobe rainbow marble from pbase bkbowden top view
(top view)
I have to say, I particularly liked his quote at 2:37 "People don't retire who are artists, they have too many ideas!"
Because I was fascinated by the idea of the elegant simplicity of this round pipe mold, simply round steel pipes, and how much it distorted/moved the colors around.
But I guessed that I would need one larger/wider than Mark Matthews, since rather than making marbles, I would be making vases.
I felt that using eight sections of 2" diameter steel pipe would work well for me, so I sketched this out using some green construction paper for the round pipes.
Round Pipe Glassblowing Mold - initial hand-made design sketch

Bill of Materials (BOM)

Description Source Price Each Qty Shipping Extended
2" diameter (O.D.) round 4130 steel tubes/pipes (.120 Wall)
This pipe is three feet long, and will be cut into one-foot sections
eBay $17.00 3 $17.30 $58.30
12" diameter round quarter-inch-thick (.250) steel disc (circle) eBay $20.98 1 $11.35 $32.33
Flat Steel Bar to hold the round pipes together and give strength
3/4 inch wide x 1/8 inch thick x 36 inch long
Because 2*pi(r) where r = 4.25 inches is a circumference of 26.7 inches
Home Depot
UPC# 030699439409
(by Crown Bolt company)
$4.21 1 n/a $4.21
Totals $94.84

Cutting the pipe into 12-inch sections using the horizontal band saw:

After using a punch to set the center point, using a drafting compass to set the circle around which the pipes will be placed:

Drawing the line segments, tangent to the pipes:

Setting up the grinder:

So everything will be square:

and then grinding the ends of the pipes:

Setting up a 4.6" diameter steel pipe as the center for even spacing, making sure everything is lined up:

Using wood shims to make sure everything is lined up before welding:

Top view too:

David Duthie starting the welding of the pipes:

Checking the alignment of the pipes:

Welding more pipes:

Finishing the welding:


At 20:48:58 December 09 2023 displayed this
glassblowing web page at last modified: February 27 2012