Monthly Archives: July 2012

Cleaning Bronze with Glass Bead Blasting

Here is a great video and article on glass bead sandblasting.

This company is using a fine glass bead to remove bronze patina from outdoor monuments, which restores them to their original state.  I would have liked to see some before and after photos of the monuments, but the article does contain a video clip where you can see (from a distance) the cleaned and uncleaned areas.

Workers from Sterling-based Mercer Lettering and Monument Works have been  sandblasting and pressure-washing the granite stonework over the past few weeks.  The granite stones also have been treated with an organic acid designed to  preserve the grass below while removing fungi from cracks in the stone.

On Thursday, they aimed nozzles at the bronze plaques and sprayed them with  fine glass particles. That removes the patina, or green and brown film, that has  developed on the metalwork over time without damaging the metal below it, said  Graeme Everson,  the company’s owner and a National Guard veteran.

“It brings back the shine of the bronze as it was when they put it up,” he  said.

The article does not discuss the size of the glass bead used, nor the exact machine they used, but the video shows the actual operator blasting.  You can therefore see the blast pot and the operator’s protective head gear which is useful for those just starting out and not familiar with protective gear.

To see the full original article by By ALISON SHEA of The Bulletin: Jewett City monuments gleam like new – Norwich, CT – The Bulletin http://www.norwichbulletin.com/news/x1474279320/Jewett-City-monuments-gleam-like-new#ixzz21poiW0in

© Copyright (c) ALISON SHEA The  Bulletin Originally Posted May 18, 2012

 

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Schematic Drawing of a Venturi Nozzle

Venturi Sandblast Nozzles Vs Straight Bore Blast Nozzles

Schematic Drawing of a Venturi Nozzle

So what is the real difference between these two types of nozzles, and why should you care?  Well, for starters, you should know that the introduction of venturi nozzles over thrity years ago still remains the last major advance in nozzle technology.  Thirty years is a long time!

You see up until the mid 1950’s, all sandblasting nozzles were straight bore.  They had a tapered converging entry, a parallel throat section, and a full length straight bore and straight exit.  Over time, blast operators noticed that as the interior of these nozzles began to wear and erode away, a larger and more efficient blast pattern resulted.  This observation led to the development of the venturi design.

A long venturi nozzle is characterized by having a long tapered converging entry, with a short flat straight section, followed by a long diverging end which widens as you reach the exit end of the nozzle.  A long converging entry introduces the air and abrasive mix into the nozzle, then is constricted into a short flat straight section, and then forced out the flared exit end.  Venturi nozzles can increase productivity by as much as 70% due to the larger abrasive pattern that results as well as due to the increase in velocity of the abrasive as it exits the nozzle.  In fact, velocity (outlet speed) of the exiting abrasive can be nearly double that of a straight bore nozzle, and this is force that cleans a surface faster!

So if you are in the market looking to upgrade your operation, perhaps changing to a venturi nozzle might be a good place to start.  More on that later…

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