5 . b . 1

GOOD PRACTICE FOR ClEANING NEW BRICKWORK

M,R, COCHRAN. P,E, Brick Assoc-iation of ,Vol'th Cal'o~ina , Gl'eensbol'o, 'I. C., V. S .A .

GOOD PRACTICE FOR CLEANING NEW BRICKWORK

Many new co~oul's and textures of c~ay face brick have

been introduced into the bui~ding mal'ket in l'ecent

years to meet the l'equil'ements of contempol'ary al'chi­

tecture .

Whi ~e al'chitect& al'e very p~eased with new shades of

tan, bl'own , gl'ey and b~ack, the bui~del' very often

finds that methods and matel'ia~s used to c~ean esta­

b~ished types of brick can pl'oduce disastl'ous l'esu ~ts

when used to c~ean new~y -constl'ucted wa~~s bui~t with

brick o f con tempol'ary co lours .

This discussion deals with the pl'oblem of cleaning the

newel' colours and textul'es of bl'ick and also looks in­

to mOl'e economical systems of cleaning new bl'ickwOl'k.

The conventional ''bucket and bJ:'Ush 1/ system has pl'oven

to be expensive in today 's high labour market and the

papel' investigates several cleaning systems relatively

new to this mal'ket.

This papel' will first point out ways for the buildel'

to build clean brick wa~~s , thus avoiding costly and

damaging c~eaning operations .

Next, three c~eaning systems are described in detai~,

providing information suitab~e fol' pl'epal'ation of

specifications for use of the systems .

A guide to cleaning a~~ types of contempol'ary brick

fo~~ows and the pape l' closes with a discussion of

ways t o l'emove white eff~orescence; gl'een, bl'own,

smoke, mud and paint stains and safe methods of

c~eaning wa ~~s bui ~ t with co~oured mortal' .

REINIGVNG VON NEVEM ZIEGELMAVERWERK

In den vergangenen Jahren wurden vie le neue Faroen

und Texturen von Fassadenziege ~n auf dem Mana ein ­

geJúhrt, um den Forderungen mode1'l'ler Architektur

gerecht zu u:erden .

WOhrend Architekten von mJdernen Schattierungen in

braun, grau und schwarz begeistert sind, findet de r

BauausfUhrende oft, dass Methoden und Materialien

zur Reinigung übZicher Ziege~n wmeerende Auswir­

kungen bei Veru:endung aus neuzeitZich gefarbten

ZiegeIn haben kannen .

Die gegenstiindZiche Diskussion behande lt das Pro­

bIem der Reinigung neuer Faroen und Texturen von

Ziege In und betrachtet gleichfalls wirtschaftliche­

re MOgIichkeiten neues ZiegeImauerwerk zu reinigen .

Die herkaTfU71Ziche Al't der Reinigung hat sich bei den

heutigen Arbeitskosten aIs zu aufWendig erwiesen.

Der Beitrag behandelt einige Reinigungssysterre , die

vemaItnism~qsig neu auf dem 'Markt sind.

Zunachst wird der Beitrag Wege aufzeigen, damit der

BauausJúhrende reines Ziegelmaue:rwerk bauen kann und

so den AufWand fü:r Reinigungsarbeiten ersparen kann.

AIs nachstes werden drei Reinigungssysteme im Detail

beschrieben und Informationen beigesteIlt, die geeig­

net sind, diese Systeme fü:r den Gebrauch zu spezifi­

zieren.

Es folgt ein Leitfaden zur Reinigung aIIer Arten von

m:>de m em ZiegeImauerwerk und der Beitrag schIiesst

mit der Diskussion von Maglichkeiten, weisse AusbIü­

hungen, gl'Ür2e, braune, Rauch, Schmutz und Malerei ,

Rückstande zu entfem en und zeigt sichere Methoden

Mauerwerk zu r einigen, das mit geJárotem Morte l er­

richtet wurde.

5 . b .1 -0

COMMENT NETTOYER EFFICACEMENT UNE NOUVELLE

CONSTRUCTION EN TERRE CUITE

Les dernieres années, beaucoup de briques de façade

de couleurs et de texture nouvelle sont apparues

sur le marché du Bâtiment, ceci pour satisfaire aux

besoins de l'architecture contemporaine.

Cependant, si les architectes sont tres contents de

ces nouvelles nuances : ocre, brun, gris et noir,

l'entrepreneur, lui, constate souvent que les métho­

des et les matériaux, utili~és pour nettoyer les ty­

pes de briques traditionnels, peuvent produire des

résultats désastreux quand on les applique pour net­

toyer des murs récents faits en briques de teintes

actuelles .

Le débat est axé sur le probleme du nettoyage de ces

nouvelles couleurs et teintes des briques et recher­

che des systemes permettant de nettoyer plus économi­

quement une nouvelle construction en briques. Le

systeme conventionnel de la "brosse et du seau"

s 'est avéré être couteux dans le monde actuel du Bâti­

ment, et cette étude examine quelques systemes de net­

toyage relativement nouveaux dans ce domaine. Elle

indique d'abord comment l'entrepreneur pourra réaliser

une maçonnerie propre qui lui évitera un trwJai{ de

nettoyage nccif et souvent couteux.

Viennent apres trois systemes de nettoyage, décrits

en détail, fournissant une. information utüe dans la

préparation des prescriptions pour l'usage de ces

systemes.

Suit un guide pour le nettoyage de tous les types de

briques contemporaines, et l'étude se termine par une

discussion sur les différents procédés qui permettent

d ' éliminer l'efflorescence blanche, moisissure,

souillure, suie, boues, taches de peinture.

Pour terminer elle donne des méthodes sUres pour

nettoyer des murs construits à l 'aide de mortier

coloré .

PRAKTIJKREGELS VOOR HET REINIGEN

VAN NIEUW METSELWERK.

In de laatste jaren werden heel wat kleuren en tex­

turen van gevelsteen op de bouwmarkt gebracht, ten

einde aan de eisen van de moderne architektuur te

voldoen.

Terwijl de architekten zich verheugen en kleuren

zoals beige, bruin, grijs en zwart aanwenden , stelt

de bouwer dikwijls vast dat de methoden en materia­

len die gebruikt worden om versgebouwde muren te

reinigen bijzonder slechte resultaten kunnen geven

op deze modekleuren.

Deze mededeling behandelt het probleem van het rei­

nigen van deze kleuren en van de modernere texturen

en zoekt ook naar meer ekonomische systemen om dit

te doen.

De gebruikelijke "emmer en borstel " methode heeft

bewezen te duur te zijn bij de huidige hoge lonen

en er worden in deze mededeling ook in deze rjch­

ting onderzoekingen gedaan .

Eerst wordt de nadruk gelegd op de mogelijkheden

zuiver te metselen, waardoor duur en schadelijk

reinigen wegvalt .

Daarna worden drie reinigingsmethoden in detail

beschreven, met informatie over de voorbereiding

en de voorschriften voor de voorbereiding van de

systemen.

Een gids voor het reinigen van alle types van he­

dendaags metselwerk volgt en de mededeling besluit

met een diskussie van de methoden om witte uit­

bloeiingen te verwijderen, groene en bruine rook,

modder en verfresten alsmede veilige methoden om

muren gebouwd met gekleurde mortel te reinigen.

INTRODUCTION

Many new colors and textures of clay face brick have been 1ntroduced into th e build1ng market in recent years to meet requirements of contemporar~ arch1-tecture .

While architects are ve ry pleased with new shades of tan. brown. gray and black, the bui l der very often exper1ences disas t rous results when he attempts to clean new colors with materials used in cleaning established types of brick.

Before outlining methods for cleaning new colors and textures, a discussfon of ways to build clean brick walls might be in order .

After the builder has gi ven consideration to good con­struction practices we will then look into cleaning systems and materials .

BUILDING CLEAN BRICK WALLS

If all bricklayers and construction personnel could learn to keep br1ckwork clean as wal l s a r e bu11t, one of the masonry construction industry's most frus­trating problems would be eliminated .

Many bricklayers do lay up clean brick wa l ls, saving the prime contractor the cost of clean1ng and, mcst important, saving for the owner and arch1tect the un­blemished appearance that was carefully planned for the structure . However. most new brickwork does re­quire some cleaning as a result of poor workmanship practices or as a r es ult of poor job housekeeping.

The subject of cleaning masonry might best be pre­ceded by a few tips on building clean b r ick walls .

1. Brick should be protected from mud when placed at jobsite. Cont ractor should provide boards,plastic sheeting ar ot her protective material when bricks are unloaded on ground .

2 .

In certain cases , brick should be comp l e tely covered for protection from weather until used .

Protect wall as work prog resses. protecting base of wa ll after the brick is la1d and protecting wall end of work day .

This includes fi rs t course of from the top at

Use sand , straw, sawdust or plastic sheeting al ong ground to prevent mud sp lashes. Mud removal is much more expensive than ground cover materials. Base protect ion also minimizes mortar dropping damages .

Wall must be covered at the end of each workday t o prevent washout of fresh joints, and to keep ex­cessive water out of the wall t o a void efflores­cence. Cove ring is also essential for cold weather protection .

3 . Scaffol d should be set far enough away from the wall to allow mcrtar droppings to fall to the ground. If scaffolds are not set away, mortar may lodge on diagonal bracing and adhere to wall. However, when scaffold brackets are used for the bricklayers platform , bracing presents no problem.

At end of each workday the boards on the scaffold closes~ to wall shou ld be removed or tilted up to dump excess mortar droppi ngs and prevent possible rainfall from splashing mcrtar and dirt from the boards on to newly laid masonry .

4. If the bricklayer follows good practices he can

5 . b .1-1

lay up c l ean brick wa l ls. Some good procedures are as follows . Aft e r spread1ng mcrtar (but be ­fore lay1ng br1ckl use trowel edge to cut mortar even with wall face . This prevents mortar from running down face of wall .

After laying b r ick , cut off excess mortar with a forward 11fting and rolling mction of trowel that will collect mort ar a nd prevent smearing of this mortar back on to brick fac e. Mortar should not be cut so that surplus drops to base of wal l.

Too l joints when morta r 1s "thumbprint" hard. After too l ing, cu t off mor ta r tailing with t rowel and brush excess mo r tar bu r s and dust from f a ce of brick . I f done too soon , bagging o r sack1ng very often rubs mo r t ar pa r t 1c l es into the bri ck face, and these partic l es a r e almost impossib l e to remo ve with conventiona l cleaning methods. Brushing is pr eferab l e . Use a bricklayer ' s brush made with medium soft hair .

5 . Keep the wall clean . After the bricklayer and mason contractor leave the job, someone needs to "guard " the completed masonry . Watch the struc­tural concrete crew , the terrazzo crew , welders , roofers , painters , landscape contractor . They don't seem to realize that almost nothing can be removed from masonry easily. Keep the mud pro­tection around base of wa l ls until final land­scaping work is being completed .

If the preceding techniques are foll owed a final clean ing should be easy . Very often a water hose with h1gh pressure nozzle will be adequate to re­mo ve the construction dust and occasional mortar smear found on wall .

BRICK CLEANING SYSTEMS

1 . Bucket and Brush Cl eaning

Bu c ket and Brush Cleanin g 1s the most widely used method of cleaning newly constructed brick walls i n both small and large jobs . A minimum amount of equ1p­ment is needed and workmen do not need to be highly skilled . Only the job foreman ar supervisor need be knowledgeable and experienced .

This method may be used for cleaning all colors and textures of bri ck. However , care must be used in selecting the proper cleaning solution for the job.

The safest way to determine the proper cleaning solution for a given type of brick is to ask the brick manufacturer for his recommendation .

Muriatic acid has been used for many years i n clean1ng red brick walls . This material is readily available and is economical . When used in a 10% solution (1 part muriatic acid and 9 parts waterl and applied un­der proper conditions it will s a tisfactorily clean most red brick walls .

The problem with this c l eaning material is that work­men toa often use solutions stronger than the recom­mended 10% maximum to make their job easier, and often fail to apply the solution under proper conditions as will be explained below. Furthermore, workmen often use muriatic acid on some types of brick that can be damaged with this acid . For these reasons many clean-1ng contractors refus e to use muriatic acid, and many architects/engineers refuse to all ow muriatic acid on the job .

Many new co mmercial cleaning compounds are marketed today that will clean new masonry as well as muriatic acid and can be used with more safety. Many of these cleaners contain small amounts of muriatic acid as

5.b.1-2

well 'as "wetting" and "buffering" agents to improve the solution's action and to minimize deterioration of mortar joints,

Listed below are some of the recommended commercial cleaning compounds:

Sure Klean 101,600 and Vanatrol

Superior BOO series

Quick Maso~ry Cleaner No, 22

The following procedure is recommended for cleaning by the Bucket and Brush Method:

While industry standards generally require masonry to be 7 days old before cleaning, it is possible to start cleaning operations 24 to 36 hours after com­pletion of masonry work, depending on type of brick and weather (dryingJ conditions.

1. Remove alI large mortar particles with hand tools before applying water or cleaning solutions. Use wooden paddles or metal scrape hoes. Chisels may be used, if necessary, to, remove hardened mortar or concrete. This is a very important point i n cleaning new masonry. Don't expect acid alone to remove large particles of hardened mortar.

2. Mask and otherwise protect adjacent metal, glass, wood, etc., surfaces as recommended by product manufacturer.

3. Saturate the wall with clean water. The area to be cleaned must be saturated as well as alI mason­ry areas bel ow.

Hose should be trained upon wall until brick ' s thirst is completely satisfied. If wall appears to be drying on surface, reapply water until workman is ready to apply cleaning solution. Failure to completely saturate the wall is a major cause of improper cleaning. Cleaning solutions containing dissolved mortar particles will be drawn into a dry masonry wall, causing future scumming and st.'aining. Such scumming from port­land cement dissolved in acid is extremely diffi­cult, if not impossible, to remove since it is in­soluble in alI acids except hydrofluoric - and this is a most dangerous acid to handle and is not recommended for use on brickwork.

A saturated wall will not draw particles from its surface into brick pores. Water is cheap, and usually free to;the cleaning contractor. Use it wastefully I

4. Apply cleaning solution to saturated wall with brush. Start cleaning at top of wall. Solution should be approved by architect/engineer and brick supplier. Concentration and method of application should be as recommended on container or by manu­facturer.

Cover small area, using long handled fiber brush. Scrub brick, not joints. Allow solution to remain on wall five to ten minutes as workmen scrub vigorously.

5. Rinse thoroughly as small areas are cleaned. To avoid rapid evaporation of water on areas being cleaned, keep crew just ahead of sunshine. This permits ideal conditions for cleaning wall, and also allows wall to dry soon after being washed, permitting crew to learn if alI the stains are being removed before going too far ahead.

A good phrase to remember in cleaning brickwork is "procedure is more important than the product used".

If these procedures are fo"llowed, cleaning should be relatively easy and trouble free.

2, High Pressure Water Cleaning

High pressure water cleaning (unheated waterJ is a relatively new method of cleaning newly-constructed masonry although it has been used for many years in masonry restoration work.

The more sophisticated high pressure cleaning systems feature a high pressure gun and nozzle with remote control switch allowing an operator to automatically apply cleaning solution while he is operating the gun over 100 feet from base unit. Dther systems provide two separate hoses, one with plain high pressure water and the other with solution of cleaning compound and water, also under pressure.

AlI units must be portable in arder to be taken within close working range of job. Some compact units are mounted on skids, wheels, trailer or placed in bed of pick-up truck. More elaborate systems are mounted in truck bed, complete with pumps, engines, acid contain­ers and water storage tanks.

Nozzle pressure is in the 400 psi t o 700 psi range and water flow i5 aroun d 3 to 8 gallons per minute.

Many wet cleaning contractors have gone to high pres­sure cleaning in an effort to reduce high labor costs associated with traditional bucket and brush cleaning systems. Most agree the new 5ystem is more efficient. However, hand labor is 5till needed in removing large particles of mortar from wall surface before apply­ing water and cleaning solutions.

High water pressure cleaning may be used on most hard­burned, textured clay brick. This includes reds, buffs, grays and other through - the-body colors.

This system is generally acceptable for cleaning lightly sanded or sand-blast textures where a fine application of sand is well bonded to the brick body.

Caution 5hould be exercised in using high water pres­sure on slurry or sandbox textures where an excessive coating of sand adheres loosely to body. High nozzle pressure may cut streaks in the relatively soft sand facing.

High water pressure cleaning may be detrimental to handmade brick, reclaimed brick and any underburnad product. Also, high water pressure can erode mortar joints under some conditions.

Although high water press~re cleaning may be used as outlined above, care must be taken in selecting a cleaning compound compatible with pumping system and with the brick to be cleaned. Some machine manu­facturers recommend that only certain clsaning com­pounds be pumped through "their units. If muriatic acid i5 to be used, they require the acid to be applied to wall with brush or orchard sprayer. Dther pumps are built to resist attack of muriatic acid solutions for rsasonable length of time.

The following procedure is recommended for High Pressure Water Cleaning:

Brickwork should be 7 days old before it is cleaned.

1. Remove alI large mortar particles with ,hand tools before applying water or cleaning solutions. Use wooden paddles or metal scrape hoes. Chisels may be used if necessary to remove hardened mortar or concrete. This is a very important step in cleaning with high pressure water.

2 . Mask and otherwise protect adjacent metal, glass, wood, etc . surfaces as recommended by product manu­facturer .

3. Saturate the wall with clean water. AlI immediate areas to be cleaned must be saturated as well as masonry areas below.

4. When thirst of wall area is completely satisfied , apply cleaning solution, starting at top of wall . So luti on must be approved previously by architect/ engineer and brick supplier. Concentration should be as recommended on contai ner .

Solution may be applied to wall with masonry clean­ing brush, low pressure orchard sprayer (30 to 50 psil or directly through high pressure cleaning unit. Application method i5 dependent upon re­commendation of architect /engineer, chemical sup­plier, machine supplier, brick manufacturer and most important of alI, the cleaning contractor who must be responsible for his work.

Experienced people in the cleaning field are of the opinion that cleaning solutions are dri ven into t he wall when applied under high pressure, remaining there to cause scumming in the future. Others, equally qualified, feel that if the wall is suff­iciently saturated before applying solution no appreciable penetration will occur. - Also, they find the scouring attack of acid-type cleaning solutions applied under pressure quickly erodes mor­tar smears, rapidly doing the same job as hand brushing.

50-degree nozzle is recommended for applying clean­ing solution under high pressure and under low pressure with orchard sprayer.

Let cleaning solution remain on wall for 5 minutes.

5. Wash wall down with high pressure water. Be sure to wash wall from top to bottom so alI dissolved rrortar particles will be flushed oH surface of ' wall.

3. Sandblast Cleaning

Ory sandblast cleaning is a relatively new method of cleaning newly built masonry, although the system has been used for many years in masonry restoration work.

Many architect/engineers prefer sandblast cleaning over conventional wet (acidl cleaning because of poesible adverse acid reactions with certain types of brick. Other designers are reluctant to permit sand­blast cleaning from fear the blasting operations will erode face of brick and mortar joints.

Sandblast operators can be compared with other con­struction tradesmen, some are artisans and others are incompetent. How8ver, with a qualified operator, prop8r specifications and good job inspection, sand­blast cleaning is as good as any other system and is often superior in many ways.

Basically, sandblast c18aning involves the following equipment: Portab18 air compressor, blasting tank, blasting hose, nozz18, operators prot8ctive clothing and hood.

Air pressure delivered by compressor to blasting tank may range from 40 lbs. to 100 lbs. per square incho Blasting tank is charged with the specified abrasive material and pressurized to force mixture of abrasive material and air into blasting hose and to nozzle.

Blasting pattern is determined by nozzle size and air pressure. Speed of cleaning is determined by type of

5.b . 1-3

abrasi ve used, nozzle SiZ8, air pressure, nozzle-to­wall distance and of course , condjtion of surface to be cleaned.

Abrasive material used in brick cleaning is usually sand, quartz, or granite and must be clean and finely graded.

Sandblast cleaning material should conform to one of two pa rti cle size gradations outlined in Brick Association of N. C. speci ficat ions .

Type "A" gradation is to be use d when the masonry is very lightly soiled, or when only a very light o r fine t extu ri ng of the brickwork is permitted. (44% to 55% passing No . 50 mesh sievel.

Type "B" gradation is used for cleaning heavy mortar stains from brickwork and where medium texturing of the masonry wall is permitted. (20% to 50% passing No . 30 mesh sievel.

Sandblast cleaning may be used for cleaning alI hard burned , non-glazed, smooth or textured brick. In­cluded in this category are reds, buffs, whites, grays, chocolates, etc.

Light l y sanded, coated, slurry, or sandbox brick should not be c leaned by sandblasting, unless cleaning cannot be accomplished by any other method, as the brick face can be permanently damaged.

Handmade or reclaimed brick may also be permanently disfigured by sandblasting.

As a further precaution, approval of brick manufacturer must be obtained before permitting sandblast cleaning.

The following procedure is recommended for Sandblast Cleaning:

Brickwork should be completely dry and at least 7 days old, preferably 14 days.

1. Remove alI large rrortar particles with hand tools before blasting. Use wooden paddles or metal scrape hoes. Chisels may be used if necessary to remove hardened mortar or concrete. This is a very important part of sandblast cleaning. Sand­blast operator would irreparably damage wall if large droppings are left for him to remove by blasting.

2. Provide adequate protection for alI non-masonry surfaces adjacent to work areas. Use plastic sheeting and "duct" tape to protect windows, doors, etc.

If possible, painting, caulking, etc. should be done after sandblast operation is completed.

3. When alI surfaces are prepared and protected, the operator can begin his first test cleaning.

He should clean a small area with the nozzle first close to wall, and then at varying distances from the wall, trying to select a working distance that will give the best cleaning job with least damage to brick and mortar joint.

Job superintendent and architectural inspector should be present at this time to confirm accept­able practice. Approved areas should be marked and identified as acceptable standard for the en­tire job.

5.b.1-4

CLEANING GUIDE

Red Brick-Textured

This category includes alI textured redthrough-the­body brick.

Brick in this category may be cleaned by the brush and bucket method, high pressure water method or by sandblasting. In the two "wet" systems a 10% solution of muriatic acid may be used, or approved commercial cleaning compounds.

Red Brick - Heavy Sand Finish

This category includes alI red through-the-body brick with various applied heavy sand finish faces.

Brick in this category may best be cleaned by the bucket and brush method, using plain water and scrub brush or with lightly applied high pressure water system, with plain water being used. Sandblast clean­ing is not recomrrended. If mortar stains are excessive use of cleaning compounds may be required.

White, Buff, Gray, Chocolate Brick

This category includes alI textured and sand finish brick with through-the-body colors other than natural red.

Brick in this category may be cleaned by the bucket and brush rrethod, or by lightly applied high pressure water system. Sandblast cleaning is also recommended except in cases where heavy sand finish is involved. In the two wet cleaning systems, no muriatic acid may be used. Only plain water and detergent, or Sure Klean Vanatrol or equal may be used.

SPECIALTY CLEANING

White Efflorescence

White efflorescence is ' a water soluble salt that is brought to the surface of masonry by evaporation of either construction water or by evaporation of rain water that has penetrated the wall.

Water used in mortar, grout, etc. will sometirres cause this "New Building Bloom". As the wall dries out, and as successive rains wash the wall, the "Bloom" should disappear.

If the masonry has received its regular cleaning and white efflorescence appears or reappears, no further action should be taken until the wall has had an opportunity to completely dry out. Application of additional cleaning solutions may only aggravate the problem at this point. Also, application of clear waterproofing materiaIs at this time may lock-in mois­ture and crystalline growth, causing more scumming and possible spalling of brick.

If efflorescence stains persist, it is likely that rain­water is penetrating the wall. An inspection of the stained areas should be made to determine if sizeable cracks or openings exist, permitting water penetration. Faulty flashing or a lack of flashing will contribute to staining.

Any large openings should be repaired. Where only very fine hairline cracks ,are assurred to be allowing water penetration, a clear waterproofing application may be the only solution to the problem short of a complete tuckpointing job.

Before applying waterproofing materiaIs, alI possible repairs should be made and alI efflorescence removed.

This may be removed by applying plain water and brush­ing the affected area. If water fails to remove stain, use diluted solution of comrrercial cleaning compounds, such as Sure Klean 600 for red brick and Sure Klean Vanatrol for alI others. Allow entire wall to dry out completely (over a period of little or no rainfall) before applying waterproofing solutions.

Green Stains

Green staining is caused by presence of vanadium salts. Color and solubility of these salts are dependent upon acidi ty of the brick. Very often green stains are brought about by wrongful use of muriatic acid or compounds containing muriatic acid. When green stains appear, brick manufacturer should be consulted before attempting to remove the stain.

Green stains may be removed by using Sure Klean 800 Stain Remover, or if the bricks have been silicone treated, use Sure Klean Ferrous Stain Remover or equal.

Brown Stains

Brown staining is caused by presence of soluble mangan­ese or iron oxides. Very often brown or manganese stains are brought on by wrongful use of muriatic acid or compounds containing muriatic acid.

If these stains are light, Brick Klenz may take them off with little difficulty.

Also, oxalic acid (one pound mixed in gallon of water) may do the job if stains are new and light in coloro

Many brown stains can be removed with Sure Klean Ferrous Stain Remover, or Sure Klean 800.

White Scum - Insoluble

Insoluble white scum is generally caused by faulty cleaning - failure to adequately sat urate wall before cleaning and failure to flus h wall after applying cleaning compound. As opposed to white efflorescence, this stain cannot be removed with detergents or regu-

, lar cleaning compounds.

Our only known method of remova l is to use Sure Klean White Scum Remover or by sandblasting.

When white scum cannot be removed, it may be obscured by brushing on a solution of Paraffin Oil and Varsol. Proportions of 25% Gil and 75% Varsol up to 50% each may successfully mask the stains.

Smoke Stains

Smoke stains can generally be removed by using one of the following cleaners:

Brick Klenz Sure Klean Restoration Cleaner Sure Klean Smoke Remover Calmal Foam Cleaner "Formula 409" Cleaner (The Clorox Co.) or equal

Follow directions found on containers.

Mud Stains

Mud stains are the most diffic ult of alI to remove.

Our only known rrethod of remova 1 is as follows:

Apply Sure Klean Restoration Cleaner(full strength ) with s'tainless steel pressurized "orchard" sprayer. Allow to remain on wall 5 minutes. Flush off with high pressure water spray. Repeat if necessary.

Sprayer nozzle should be held at 90 degree angle to wall, as should rinse water nozzle.