I am producing a theatrical show, and all the props that will be used
in the production consist of a steel skeleton covered with an outer
skin of styrofoam insulation (the type that can be purchased at a
store like Lowe's in 4'x8' sheets).  The fire marshal is requiring
that all the props be coated with a fire retardant, so that if a flame
is held to the styrofoam for 10 seconds, it will not burn.  I need a
flame retardant that will not only accomplish this, but also something
that can be painted on with a brush and is clear with a flat finish,
so that it will not affect the color of the props (which have already
been painted.)  I am looking for something other than Rosco Flamex
P50, which I have already ordered (I need a second product to use as a
backup, if the Rosco Flamex does not work).

Thanks for your help, a generous tip promised for a product that really works!

Hello floridaguy, 

Most any fire retardant product intended for use in theaters and
public places must meet the ?10 second ignite? test. The products
contained in this answer state they all meet fire safety standards,
and most are listed as being used in public places. Before you order,
please speak to the company representative to verify that their
product will meet your requirements.

I?m glad you mentioned at the beginning that you had already ordered
Rosco Flamex P50, as that is the first thing I found when conducting
this search!
However, Rosco makes another product, specifically for Styrofoam,
called FlexBond, that dries clear.


=========
Rosco
=========
?Rosco FlexBond is a clear, flexible scenic glue which bonds many
porous and non-porous scenic materials.  Rosco FlexBond dries to a
clear, hard, yet pliable coating that does not suffer from the
"tackiness" common in many other flexible glues, even after those
glues have had days to dry!  And unlike ordinary "white" glues which
crack and break when flexed, the adhesive bond of Roscoe FlexBond
remains extremely pliable and strong even as the materials bend and
deform.  Roscoe FlexBond is water-based and safe to use, available in
gallon jugs or five gallon pails?
#7653  One Gallon...$26.25
#7654  Five Gallon...$119.65


Also, ?Rosco Flexcoat is a flexible, nontoxic, water-based coating for
polyurethane foam, Styrofoam, and ethafoam. Its 100% acrylic
formulation provides excellent adhesion to a wide variety of
substrates. Flexcoat contains no plasticizers, so it will not be
brittle withage or exterior exposure. It is compatible with all Rosco
paints used either as tints or surface coatings. Flexcoat is
weatherproof and flame retardant, providing one coat protection for
all of your theatrical applications; available in gallon jugs or five
gallon pails.?
#7655 One Gallon...$41.50 
#7656 Five Gallon...$185.50
http://www.theatrehouse.com/en-us/dept_168.html


?Add P50 to Rosco Clear Acrylic to create a fire retardant clear
sealer.? And ?Rosco gives the following method for testing a flame
retardant treatment: Hold a completely dried three-inch-wide strip of
fabric vertically, and light the lower edge for ten seconds with a
butane lighter, propane torch, or long wooden kitchen match. The
material should ignite, but after the flame is removed, sufficiently
treated material should self-extinguish within five seconds.?
http://www.pnta.com/5.html
 

=======
WT-103
=======
WT-103 is a Class B interior, intumescent, latex, clear, flat coating
for interior use. Non-hazardous, non-toxic, non-carcinogenic
formulation. Application over wood, fiberboard, plasterboard,
cardboard, foliage and other decorative surfaces. This product works
on many types of surfaces that require a clear, flat flame-retardant
coating.
http://www.firetect.com/wt103.htm
http://www.firetect.com/


==========
Snuff-it
==========
Another product is Snuff-it
Snuff-it 5
 http://www.productionadvantageonline.com/SNUFF-IT.htm
FLAME RETARDANT, GAL., WATER BASED ACRYLIC LATEX PAINT ADDITIVE. Use
for coating non-porous substrates such as foams, plastics or
previously painted scenery.
$138.24  for one gallon
http://www.productionadvantageonline.com/otherpaints.htm#FLAME%20RETARDANT

===========
Flame Stop
===========
According to this product selection guide, Flame Stop IIA or I-DS
would be the one to meet your needs.
http://www.flamestop.com/html/fire_retardants.html

http://www.flamestop.com/html/product_guide.html

Flame Stop IIA
Flame Stop II-A? is a pyrolitic, intumescent formulation that prevents
the spread of flame by developing a chemically self extinguishing
reaction and creating a carbon crust on the surface of the hazard.
Flame Stop II-A? can be used either for interior or exterior
application. Flame Stop II-A? is a surface coating chemical that is
white in appearance, however dries clear.

Flame Stop II-A? is recommended for use on hard non-absorptive
surfaces such as paneling. Spray application generally provides
superior surface coating, however, brush or roll application method is
also acceptable based on United States Testing Report #LA62466.
http://www.flamestop.com/html/fr_i_ds.html
I-DS
Flame Stop I-DS? is a pyrolitic formulation that prevents the spread
of flame by developing a chemically self extinguishing reaction. Flame
Stop I-DS? is a clear penetrating chemical.

Flame Stop I-DS? is recommended for use on various substrates such as
thatching, mulch, bamboo, foam rubber, open cell and closed cell foam
rubber, nylon netting, exterior composition siding and many other
difficult to treat materials. This product is a Class A rated fire
retardant and can be used for exterior purposes. It can be applied by
either dipping or spraying and can be topcoated with any latex paint
system.
http://www.flamestop.com/html/fr_i_ds.html

============
Fire-Shield
============
Fire-Shield Products
This site is written in frames, so you must use the navigational links
and menus to visit areas of interest.
Fire Shield products used in Cape May Performing Arts Center, Syracuse
University and the San Diego Ballet, to name a few.
http://www.nyfs.com/ 
Formulation designed to protect plastics, fiberglass, Formica, most
all smooth surfaces. Dries to a hard gloss finish.
http://www.firechemicals.com/

============
Turning Star
============
http://www.turningstar.com/
Products
http://www.turningstar.com/products.html

=======================
Nochar?s Fire Preventer
=======================
This one seems unlikely to be what you need, but I?m including it for
you to decide.
Nochar Fire Preventer is a non-toxic, non-hazardous fire retardant for
all unsealed natural fiber materials and products (MSDS available).
Unsealed natural fibers include but are not limited to cotton, wool,
silk, rayon, linen, paper, cellulosic fibers and wood. "NFP" contains
no coloring agents, thickeners, or inhibitors (non-toxic dyes may be
added). "NFP" may be applied by spray, curtain coating, thermal dip,
vacuum chamber, roller coating. brush, or soak. Nochar's Fire
Preventer is a water-soluble product that uses water as a carrier to
penetrate the fiber. The water is then dried off or driven off,
leaving the retardant in place. Recommended rate of application for
most species of dimensional lumber is brush or roll on-150 feet per
gallon, airless spray up to 300 square feet per gallon, fogging
method-up to 500 square feet per gallon. Note that these coverage's
may vary by species of wood and the moisture content. Paper and
textiles must add 40% by volume weight of liquid fire retardant.
Nochar's Fire Preventer increases the fire safety of materials and
products treated by increasing the combustion temperature of natural
fiber materials. "NFP" reduces the rate of heat release after
ignition, and slows the rate of flame spread. Should a fire start from
other fuel sources, "nochar's Fire Preventer will slow the progress of
the flame on the materials that have been properly treated with the
product. Nochar's Fire Preventer is used extensively for on-site
treatment of construction projects, industrial plant safety,
packaging, the creation of new products with better fire performance
characteristics, and in agricultural application. Uniforms can be
treated during the laundry operation for extended life and for greater
employee safety. Nochar's Fire Preventer is also being used in the
manufacturing of latex paint to improve the fire performance of all
types of surfaces for commercial or home environments. Nochar's Fire
Preventer may be added to other types of coatings, bonding agents,
adhesives and sealants.
$129.50 for 5 gallons
http://www.halloweenplus.com/index.cfm?Page=products&Nav=products&Category=1300&Sub_Category=1310&Product_Number=6902



You probably already know everything contained in the next links, but
I?m including them, on the off chance  you may find them interesting.
(I did!)
http://www.singaporetheatre.com/technical_theatre/theatre_safety/fireretard.htm
http://www.singaporetheatre.com/technical_theatre/theatre_safety/fireretard.htm
http://www.singaporetheatre.com/technical_theatre/theatre_safety/theatresafety.htm


I certainly hope you are able to select an appropriate product from
this answer,and I wish you well with your project!  If any part of my
answer is unclear, please ask for an Answer Clarification, before
rating. This will allow me to assist you further, if possible.

Regards,
crabcakes

Search Terms
Theatrical fire retardants

Thanks for the comprehensive answer.  The Rosco P50 (which I had
already ordered) worked fine, so I didn't need to try any of the
products you suggested.  But thanks for the help.

If you have ever seen a lot of styrofoam burn at once, it is an
instant fiery hell.  It sounds like you are already done with this
one, but in the future if you are concerned about fire you might try
another material.  Sheet rock/drywall, osb/plywoods, and various
wallboards/panelling - they are all better around fire than styrofoam,
and easy to cut with the right tools.

Break a leg...