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A Guideline for Design

Sandblasting glass is not an exact science. There are many variables that can detract from a uniform appearance. Milestone has taken to task the objectives of providing pristine, uniform appearance in sandblasted and sealer-coated glass, quick turn around times, new products and great customer service.

Sandblasted glass offers flexibility and options in design and appearance that other products just cannot provide.

As time goes by we find that the search for new, distinct sandblasted finishes for unique appearances in architectural interiors and exteriors are frequently pushing the limits of technology and product development. Milestone is currently engaged in testing products, tools and procedures to find these new finishes. Some times we have great success and some times great failures, the failures are simply a way of learning what not to do and point us to reviewing the steps taken and then revising the approach. Some of the new textures and patterns are breathtaking, some are good only for specific applications and others are just simply too expensive to produce. The latter causes yet another opportunity to look for cost saving ideas without compromising the quality we expect.

The following is information about sandblasting and sealer coatings and some of the things we have learned over the years that can be useful in designing projects that push those limits of product and technology. It is given as a guideline to avoid falling into proven traps and to steer thoughts and energies into areas that have potential for development.

Extreme coarse textures and carving on tempered glass or glass that is going to be tempered is one of the areas most frequently challenged. The more surface area of the glass that has a coarse texture or depth carving, the more likely the glass will break in process. Milestone has developed a fair sense of what those limits are. We are always willing to engage in finishes that have more risk if the requesting party assumes the cost liability. Another area of information centers around the bow that occurs when tempered glass is completely blasted on one side. The general rule here is that the thinner the glass the more the bow is evident. Also, the deflection will be greater when the difference in the ratio of length to width increases. Deflection reduces as the percentage of clear or non-blasted area increases. A square, thick piece of tempered glass with a clear border will have the least evident bow.

With the advances and availability in laminated glass products, depth carved sandblasting and coarser textures can be facilitated and still maintain a safety glass rating to meet building code requirements. (Sometimes city, county and state building codes will allow installation of non-safety glass in areas usually required to meet safety glazing requirements by using an "art glass" exemption. This circumvents the need for tempered or laminated glass to be used and allows for more flexibility and design to create the desired effect and finish. You should check with your local authority before proceeding on any job of this nature and getting written pre-approval.) Laminated glass can become very brittle as a result of the sandblasting process for several reasons. First, laminated glass can have an inherent "built in" stress factor as a result of the laminating process. This stress in the glass is not usually detectable to the human eye and becomes evident when the glass cracks for no apparent reason, minutes, days or weeks after blasting, but this is rare. Secondly, if laminated glass is fully blasted on one or both sides it is easier to break. Thirdly, depth carving that goes to the edge of the glass can create a point of breakage that can be avoided by simply utilizing a clear border in the design.

In general terms, the higher the ratio of clear surface to that of the sandblasted surface on any given lite of laminated glass will reduce the risk of breakage and increase its' durability.

Sealer coatings are another scope of work that Milestone pays particular attention. We start first with the premise that sandblasted glass has an inherent need for different care and cleaning than that of other glass products. Continuing with the knowledge that raw sandblasted glass can look horrible in a very short time when exposed to fingerprints and contamination, with the understanding that sealer coating the glass can reduce or eliminate the negative effects of regular wear and tear. There seems to be a split in the industry when considering the durability of the sealer coating compared to the appearance of the sealer coating once it is applied to the sandblasted glass surface. It is Milestones' position to use a sealer coating that has high durability and the best appearance. Other products on the market used by other sandblasters are positioned to be indestructible with less attention paid to the overall appearance on the sandblasted areas of the glass. These products "cover up", "fill in" and generally eliminate the texture and unique appearance of the sandblasting surface, giving no visual evidence that the glass was ever sandblasted. The sealer coating that Milestone uses can be damaged from improper cleaning. This is generally overcome by our policy to get the cleaning and handling instructions to the transportation, installation and building maintenance personnel that are involved with the sandblasted glass in the time period from our shop to job completion and beyond. Milestone takes great pride in our ability to furnish and install a sealer coating that is not generally detectable on the sandblasted surface, thus allowing the visual emphasis on texture and pattern, while at the same time doing double duty in reducing fingerprints and contamination and facilitating easier cleaning. More about sealer coatings can be learned from the information on our web page at milestonemfg.com, under the heading of news and notes.

The flexibility of sandblasting on one or both sides of glass can offer a very distinct and unique appearance. It really becomes a statement of individuality for the visual aspect of corporate identity. Milestone can offer assistance in design ideas that can accommodate the needs of the workforce in the daily routines of the work place and still make an architectural statement. This statement can be one of high drama or understated elegance. Sandblasting can also address the issues of office security where glass is used in the lobby, conference rooms and office space areas. With shapes and patterns that bypass the doldrums of inferior products, sandblasted glass launches design and imagination to a new level of spectacular beauty. When considering the specific subject of double sided sandblasting, it is our opinion that the design possibilities are unlimited. Watch for Milestone to be reaching new limits as product and ideas come together.

Let's look at the textures created by the impact of the sand or blasting media contacting the surface of the glass. This texture actually consists of chips or abrasions in the surface of the glass. Talking in very specific detail, the smaller the chip the finer the texture, the larger the chip the coarser the texture. Some finishes can actually utilize two different textures of sand, blasted in two processes to create the desired effect on the glass. Our extra fine etch is a finish for all glass types and thick nesses, it is very valuable for use in areas where sealer coatings are not going to be used and easier cleaning is required from a sandblasted surface. It is also used as a foundation base for other finishes. Our standard etch is a fine etch, widely accepted and used in the industry. It reaches its' greatest potential when sealer coating is applied. The standard etch is used on a types of glass with the only exception being that when applied to eighth inch tempered glass products we turn the compressed air pressure down to help avoid breakage. Because of the reduced pressure, blasting time is extended which leads to a higher production cost a good reason to design using a slightly thicker glass. Looking at our medium etch, this is good for jobs requiring a bolder texture. It can be applied to all annealed glass products and tempered glass products one-quarter inch thick or heavier. Next is the coarse texture, recommended for all annealed glass over one quarter inch thick and for tempered glass products three eighths inch thick and greater. This is the limit of what you will see in our standard sample sets of textures but not the limit of what we can do. Our ability to blast with media that is up to three sizes larger, allows us the opportunity to facilitate a complete spectrum of finishes. There is specific benefit and drawback associated with using these heavier textures. First, they are very risky to use on tempered glass products, second, they are destructive to expensive finished edge treatments similar to those found on custom table tops or the polished edgework used in butt glazed glass partitions and glass shelves. The benefit coming from the magnificent appearance as the heavy texture sparkles and shines in the changing light. Sealer coating is recommended for the heavy textures too. As textures change, the materials for stencils and masking change too. Milestone can accommodate most desired finishes. Keep in mind that one of the side effects of using heavier sand is that edge plinks are going to be more evident and abundant on finished glass surfaces and edges. This might suggest that the blasting process be done prior to other fabrication to eliminate the plinks, this can get complicated quickly when you throw in the need for a sealer coating and the other contingencies of timing and fabrication procedures. Coordination and cooperation between glass fabricator and glass sandblaster now becomes a key element in accomplishing the job at hand.

Let's look at custom stencils, Stencils can be made by several processes, they can be hand cut, computer cut and made by a process called photo resist. Computer work requires an electronic file to be used. These e-files are most usable when in an EPS format for PC. EPS files are basically line drawings or vector files. There is an option for "fixing" or modifying unusable files. Files are most often found unusable when they contain one or more of the following features, extra lines, "layers" of lines, lines not connecting, lines missing and lines overlapping. Stencils are used to keep certain areas of the glass clear during the blasting process. It is important to choose the correct type of stencil for the job required.

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