FREQUENTLY ASKED QUESTIONS
1. How and where is
this product made? Is it made like ceramic tile?
Astra-Glaze-SW+ units are made in Emigsville, Pennsylvania,
and Phoenix, Arizona. They are made using high purity, natural
grain silica sands and a resinous binder cast onto a concrete
block in a thermoset, glazing process. The result is a hard
glazed tile-like surface permanently molded onto one or more
faces of the concrete blocks. Astra-Glaze-SW+ blocks are fired
at about 500 degrees Fahrenheit in a tunnel oven.
Conversely, ceramic tiles are fired at about
2,000 degrees Fahrenheit. Because Astra-Glaze-SW+ facings
are permanently molded to concrete blocks, they cannot come
off without destruction to the concrete block itself. Ceramic
tile, on the other hand, is a thin fragile layer that is glued
on by tile setters after the wall has been erected and can
be removed more easily.
2. Can Astra-Glaze-SW+
blocks be used on the exterior of buildings? Will they deteriorate,
fade, crack or spall?
Astra-Glaze-SW+ units have been used to construct interior
and exterior walls of buildings in almost every part of the
continental United States for more than 32 years with excellent
Important Note: As with any
building material, it is important that the building design
and workmanship be correct. For example, if the units are
laid in the wall such that the concrete block substrate is
continually saturated with moisture (in the winter months
in northern climates) due to inadequate flashing or coping,
poor mortar joints, leaking water pipes, etc., then the constant
freezing and thawing action can eventually cause crazing.
Of course cracking, due to settling or wall movement can also
allow large amounts of moisture to enter and saturate the
concrete blocks, causing the same problem. Good masonry building
practices and workmanship (including well tooled joints) should
be specified and enforced. Proper specification and installation
of flashing, coping and weep holes are essential to satisfactory
performance and adequate control joints or other devices to
accommodate wall movement should be employed. The recommendations
of NCMA TEK Notes should be followed. The glazed facings of
Astra-Glaze-SW+ and units are unaffected by acid rain or by
temperatures up to 400° F.
3. How do Astra-Glaze-SW+
units perform in extreme cold, heat (i.e. kitchens near grills),
sunlight or acid rain, etc.?
Astra-Glaze-SW+ blocks perform excellently in a wide
range of wall applications including kitchens, laboratories,
chemical plants, etc. and in the presence of acid rain.
4. Do the Astra-Glaze-SW+
facings meet Federal Agriculture (i.e. Department of Agriculture)
Standards for food processing, etc.?
Astra-Glaze-SW+ facings meet all federal, state and
local standards for chemical resistance, stain resistance,
fire, flame, smoke, etc. The federal specification is ASTM
C744. It meets the Department of Agriculture standards for meat-packaging plants and other
5. What does the "SW"
stand for in Astra-Glaze-SW+?
SW stands for SEVERE WEATHER. Astra-Glaze-SW+ units
are a product of state-of-the-art technology and advances
in polymer chemistry that have enabled Trenwyth to make its
quality products even better.
To withstand all weather conditions from northern
hard freeze to southern intense sunlight (UV), Trenwyth’s
block glazing chemistry has been designed to accommodate both
extremes and everything in between.
A degree of ductility has been built into the
Astra-Glaze-SW+ facings and only fully cured, completely dry
lightweight blocks conforming to ASTM C90 are used for glazing,
thereby giving the finished Astra-Glaze-SW+ units exceptional
resistance to cracking and crazing. Glazed units manufactured
in Arizona are mediumweight units. Ultraviolet light inhibitors
and stabilizers are built into the Astra-Glaze-SW+ chemistry,
allowing the facings to maintain their color. All units contain
Trenwyth-approved integral water repellent CMU admixture at
the time of manufacture. The backup block is integrally damp-proof
preventing water from being absorbed and held behind the glazed
facing. If moisture does get into an Astra-Glaze-SW+ wall,
the water is not absorbed by the block but is shed, flowing
down the wall to be collected by the flashing and directed
to the exterior through weeps or vents.
Colorfastness has been achieved through chemistry
that blocks ultraviolet light from penetrating the facing
and stabilizes the polymers. This prevents degradation of
the Astra-Glaze-SW+ facing.
6. What does the “+”
stand for in Astra-Glaze-SW+?
Astra-Glaze-SW+ glazed masonry units have always been
a low maintenance product. Trenwyth formulated a process that
makes Astra-Glaze-SW masonry units even more graffiti-proof,
and have reintroduced them as Astra-Glaze-SW+ units. New built-in
protectants in the PLUS units act as an invisible shield that
withstands spray paint, permanent markers, grease and crayon.
7. Are Astra-Glaze-SW+
No. Astra-Glaze-SW+ facings are classified as non-toxic.
The only standard for toxicity is the New York City Material
and Equipment Acceptance Division (MEA) toxicity requirement.
We have passed this standard. Our approval number is MEA 31-82-M.
8. What are industry
standards for glazed blocks, ASTM, etc.?
The ASTM standard for glazed concrete blocks is ASTM
9. Are they “UL”
Astra-Glaze-SW+ blocks are tested annually to Underwriters
Laboratories (UL) equivalent standards by various independent
testing laboratories. Therefore, they are UL rated although
they are not UL listed. There is no requirement that glazed
blocks be UL listed in the United States.
10. Can special colors
We can match virtually any color.
11. How is your color
consistency and will it match if we do a later addition?
We match our color standards to very close tolerances.
Add orders or additions to older installations can be matched
if we are provided with a sample.
As with any manufactured item, a minor variation in shade
is to be expected. With Astra-Glaze-SW+ units, we have reduced
this to a minimum. The color of the Astra-Glaze-SW+ surface
is required to conform to an approved standard, tested and
verified by a spectophotometer.
12. Can we get two different
colors on one block?
Yes, we can put any color on one side and the same
or any other color on the other side of the same block.
13. Can special sizes
and/or shapes be made?
We can make a variety of special sizes and shapes.
However, molds can be very expensive. By charging an additional
fee we can accommodate many special shape requests.
14. Can you provide double
We cannot provide double bullnose units because they
cannot be drawn out of the molds: the molding methods we use
will not accommodate double bullnose units on full sized blocks.
We do, however, supply some double bullnose units in our 1"
and 2" Shapes Series.
15. Why can’t two
faces and one end be glazed?
We cannot glaze two faces and one end because it would
be impossible to draw such a finished product out of the mold.
We can only make one face and an end or we can make one face,
one end, and one top, but we cannot make two faces and one
16. Can special scoring
Special scoring can be done. We require a sketch or
written dimensions in order to produce the special scoring.
There are certain limitations, however, and we generally don’t
advise more than five vertical scores and not more than two
horizontal scores on any face of any block. We have difficulty
scoring around bullnose comers and caps. This is very expensive
and time consuming but it can be done, so you should check
with customer service or the sales department to make sure
that any special scoring patterns can be made.
17. What is the width
of the score and is it cast or cut?
The width of the score on the Astra-Glaze-SW+ face
is 1/4" and it is cut after the glazed face is molded.
18. Can I get the backside
of the exposed block scored to match the scoring on the glazed face side?
The backside of the blocks can be scored to match the face. This score, however, is 3/8" wide which is standard for raw blocks.
19. Do I tuckpoint the
All scored joints must be tuckpointed to prevent moisture
penetration and to match the real joints between the blocks.
The result is a more realistic pleasing finished wall appearance. DO NOT USE RAKE JOINTS unless tuckpointing with epoxy.
20. Can I have an Astra-Glaze-SW+
face on one side and a Trendstone finish on the other side
of the same block?
No, an Astra-Glaze-SW+ and Trendstone finish cannot
be on the same block because of differences in block density.
We will not cast Astra-Glaze-SW+ facings onto heavyweight
or normal weight blocks. Astra-Glaze-SW+ facings must be molded
onto lightweight or mediumweitght blocks to get a strong and
integral bond. The surface of heavyweight blocks is generally
less open, preventing a good mechanical bond between the facing
and the block. Therefore, heavyweight blocks do not stand
up very well to freezing and thawing in exterior applications.
Lightweight blocks perform well in freeze/thaw conditions
because the aggregate used (expanded shale or expanded clay
in our case) is cellular in nature, giving blocks made with
them a good measure of ductility.
21. How do Astra-Glaze-SW+
blocks compare to structural glazed facing tile (SGFT); are
there any advantages or disadvantages?
SGFT is available in Standard 8W Series which provides
no fire rating or in 8WC PR Series which gives a one (1) hour
fire rating for a 4" wall. The fire rated units are priced
so high as to be noncompetitive with Astra-Glaze-SW+ units.
Standard 8W SGFT units are competitive with
Astra-Glaze-SW+ units in the 2" and 4" thicknesses
but are much higher priced in 6" and 8" thicknesses
(and in the fire rated units mentioned above) and are not
available at all in 10" or 12" thicknesses.
Having a vitrified, ceramic glazed surface,
SGFT is slightly more chemical and stain resistant than Astra-Glaze-SW+
units. However, like china, it is much more brittle and more
easily damaged by impact. And unlike the smooth, even finish
of Astra-Glaze-SW+ units, SGFT surfaces tend to distort during
manufacturing, resulting in a wavy look when installed. Additionally,
the color consistency has traditionally been poor.
22. How do you patch
Contact Trenwyth Industries for an Astra-Glaze-SW+
Patch Kit. Small scratches and scuffs can be removed by using
a 50/50 mixture of boiled linseed oil and turpentine mixed
well together and wiped on with a clean rag. After a few minutes
the excess should be removed with a clean dry rag or a paper
towel. Be careful not to get this mixture into the joints
as it will darken the mortar.
23. How do I cut Astra-Glaze-SW+
blocks in the field? Are there special tools required? Will
the surface splinter and chip when cutting?
Trenwyth produces most of the shapes and sizes needed.
Cutting should be done only when absolutely necessary. It
is best to cut Astra-Glaze-SW+ blocks with a motor driven
power masonry saw using a wet diamond blade. There are some
dry diamond blades that perform acceptably without cooling
water. There are also abrasive blades that can be used in
these power saws. The glazed surface will not splinter and
chip if care is exercised and the above recommendations are
24. How well does the
product withstand graffiti and how is it removed?
The Astra-Glaze-SW+ surface withstands graffiti very
well. Graffiti can generally be carefully removed using Trenwyth’s
Graffiti Wizard® environmentally friendly cleaner (see
25. What do I use for
See Astra-Glaze-SW+ Cleaning Instructions.
26. What type of mortar
can be used?
Astra-Glaze-SW+ blocks should be laid in a full bed
of mortar which is consistent with the best concrete masonry
practices carefully following the recommendations of NCMA
TEK Notes for best results. All exterior mortar shall include
a Trenwyth-approved integral water repellent additive added
to each batch in the appropriate dosage rates for mortar type
(M, S or N) per manufacturer’s instructions.
27. Can I return blocks
I don’t use?
No, all Astra-Glaze-SW+ blocks are custom made to order.
We require a signed Sales Contract before we will start manufacturing
any order. Since we don’t make any blocks for stock,
any Astra-Glaze-SW+ blocks that are ordered in excess must
be taken and cannot be returned. It is strongly recommended
that great care be taken with “take-offs” to avoid
28. Can a face be supplied
without a block attached to it?
No, we cannot supply a face without a block attached
to it. The minimum thickness of block we can make is a 2"
unit and that can usually be used in any thin veneer situation.
29. Will the face pop
off (typical of glazed brick)?
The Astra-Glaze-SW+ face will not pop off. The face
is an integral part of the block once it has been molded and
cannot be removed without destruction of the basic block.
30. How do we deal with
the “ledge” created by Astra-Glaze-SW+ blocks
when painted CMU’s are laid above (i.e. walls with
The 1/8" ledge created by Astra-Glaze-SW+ blocks
in such an application is actually very attractive. If the
mason lays the walls so that the glazed surface protrudes
1/8" beyond the painted CMU above, it can actually enhance
the overall appearance. Conversely, the units can be laid
flush to the face if the ledge is not desired. (Then the 1/8"
protrusion will be at the back of the wall.)
31. Can any mason install
Masons who are used to laying architectural blocks
can lay glazed blocks very well. Unfortunately, no matter
how well our blocks are manufactured, if they are not laid
well, the appearance of the project is diminished. Astra-Glaze-SW+
must be laid to the face.
32. Can water go through
the Astra-Glaze-SW+ face?
No, the face of the Astra-Glaze-SW+ units is impervious
to water. Tests have been conducted using high-pressure stream
and no measurable penetration was recorded. All blocks used
for glazing contain Trenwyth-approved water repellent additive
to provide additional protection should water penetrate the
wall through the mortar joints. Note: Any scores on the face
of Astra-Glaze-SW+ blocks must be tuckpointed or water will,
of course, penetrate through the scores.
33. Why choose Astra-Glaze-SW+?
|ASTRA-GLAZE-SW+ offers you:
- highest standard for quality
- Pre-consumer recycled content
- the advantages of block construction
- Tremendous variation of color, pattern and design
- Prompt delivery from large, efficient regional plants
- USDA approved for sanitary environments
- Finished load-bearing walls
- Fire protection built into your design
- One trade installation cost savings
- Custom color matching capabilities
- Available in Acousta-Wal sound-absorbing units
Modern technology has created many new building
materials with properties and performance characteristics
never before obtainable in so called “natural”
materials--Trenwyth’s Astra-Glaze-SW+ units are an example
of such progress.
Recent improvement in technology allow for the
stain-resistant, chemical resistant, non-fading and fire resistant
structural glazed masonry units which are manufactured today
by Trenwyth Industries under the trademark Astra-Glaze-SW+®.
Channels of Distribution: Astra-Glaze-SW+
units are manufactured at two locations in the United States
and distributed through Trenwyth’s regional sales offices
and a network of dealers throughout the United States, Canada
and the UK. Most of the Astra-Glaze-SW+ dealers are large
block manufacturers or brick distributors serving every part
of the U.S.
High Quality Standards: There
is one uniform, high standard for all Astra-Glaze-SW+ units—Grade
A1. There are no seconds, no unselected grades, no off-grade
industrial classification. Just Grade A1!
Variety to Meet Your Design Needs: Consider
the first advantages of the unit itself — the surface
is a smooth satin finish available in 96 Standard colors plus
custom colors. The 8" x 16" face size means approximately
one unit per square foot. Face sizes are exact and permit
precise coursing and uniform 1/4" joint size. Face modulation
is negligible. This gives a smooth, even appearance to the
glazed wall surface. Astra-Glaze-SW+ facings are available
on virtually every size and shape of concrete block (for example,
cove base, jamb, bond beam, cap units, etc.). This allows
a wide latitude and flexibility in design and methods of construction.
In addition to the usual glazed shapes and trim
units, Astra-Glaze-SW+ brings to the designer the Scored Series
and the Design Series which offer a wide selection of scale
and pattern. The Scored Series provides the choice of reduced
scale and pattern with the economy of large 8 x 16 block,
e.g. 8 x 8 Score (DA 1) 5 x 8 Score. (DA5) Brick Score (DA3),
The Design Series includes various curved and
flared projections on the faces to give form to the wall.
Cost Savings: The economies
inherent in Astra-Glaze-SW+ construction become very clear
when you analyze the erection of a loadbearing wall.
In the case of ceramic tile, the mason lays
up the block wall and another tradesman, the tile setter,
lays up the ceramic tile in a separate operation and, in a
further operation, grouts the joints. In the case of epoxy
coating, the mason lays up the block wall then another tradesman,
the painter this time, applies a filler coat plus two finish
Astra-Glaze-SW+ units, however, are laid up
by the mason in one operation providing both the structural
wall and the finished surface. Furthermore, Astra-Glaze-SW+
facings are permanent. They will last the life of the building,
will not fall off or ever require resurfacing. No matter what
thickness of loadbearing wall, the masonry contractor can
lay one through-wall unit with Astra-Glaze-SW+ units.
Ease of Construction: In modern
construction, today’s designer is faced with a host
of problems involving electrical conduits, gas pipes, water
pipes, waste stacks and other utilities running through the
building. In schools, hospitals, laboratories and industrial
plants, a designer may have to deal with compressed air lines,
oxygen systems, etc. as well.
Plumbing, wiring, gas pipes and waste stacks
are easily accommodated in Astra-Glaze-SW+ walls. The Astra-Glaze-SW+
finish is easily drilled or sawed to receive the electrical
plumbing or other outlets.
Fire Safety: Truly adequate
fire protection with a factor of safety is of vital concern
to every designer of schools, hospitals, dormitories and multi-story
buildings. Astra-Glaze-SW+ units give you that required fire
rating up to 4 hours, which is the rating of the block itself.
The glazed facing itself is classified as non-burning.
The ASTM and Federal government Specifications allow a flame
spread of up to 25 and a smoke contribution of 50. Astra-Glaze-SW+
tests at 5 flame spread and 25 smoke contribution. This means
that our glazed unit greatly exceeds the requirements for
In Summary: Astra-Glaze-SW+
offers you prompt delivery from large efficient regional plants
and personalized service. You get the cost savings of a single
unit being both structural and finished. The glazed finish
meets the highest standard for quality — and exceeds
all the industry standards. Astra-Glaze-SW+ units bring all
the advantages of block construction with tremendous variation
of color, pattern and design. With Astra-Glaze-SW+ units,
the entire back-up wall can be eliminated. Important, too,
is the fact that you provide recognized fire protection in
If you have any questions, please contact Trenwyth
Industries at 800-233-1924 to find the representative
in your area.