JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 1:203-204 (1984)

A TECHNIQUE FOR ACHIEVING CONSISTENT RELEASE OF FORMVAR FILM FROM CLEAN GLASS SLIDES

C.A. Edwards*, G.K. Walker+, and J.K. Avery*

* The U n l v e r s l t y of Mlchlgan Denta I Research I n s t 1 t u t e and School of D e n t i s t r y Faci I l t y for E lec t ron Mlcroscopy 1011 N. U n v i e r s i t y Ann Arbor, M I 48109 (313) 763-4255

+ Eastern Mlchlgan U n i v e r s l t y Department of B I ol ogy Yps l l an t i , M I 48197

The use o f Formvar ( p o l y v i n y l formal) coated g r i d s f o r support ing

specimens such as bacter ia , v l ruses, very t h i n sectlons, and particulate

matter has become canmon p r a c t l c e I n Transmission E lec t ron Microscopy (TEM).

The primary d i f f i c u l t y I n o b t a i n i n g s a t i s f a c t o r y r e s u l t s has been ttcoaxinglf

t h e f i l m o f f o f t he microscope s l i d e onto a water surface. This problem can

be overcane by p r e t r e a t i n g microscope sl ides w i t h Vlctawet l ; a c m e r c l a l l y

a v a l l a b l e we t t i ng agent. The procedure invo lves t h e f o l l o w i n g steps:

A )

B)

C)

Dlp microscope s l l d e s l n absolute ethanol and wlpe dry. Place these

as ide i n a v e r t i c a l p o s l t l o n t o minimize l i n t and dust accumulation.

Place a small p iece o f Vlctawet ( l m m 3 ) I n a tungsten w l re basket

(whlch has been prev ious ly secured I n a vacuum evaporator) uslng

f i n e forceps,and fo rce the VTctawet gent ly towards t h e b o t t m , or

conlca l end.

Place two or th ree c lean microscope s l i d e s dlrect.lv under the

tungsten w l r e basket, a l l o w i n g a d is tance of two inches between t h e

basket and s l i des . Close t h e b e l l j a r and evacuate t o proper

operat ing vacuum.

' a v a i l a b l e fran: E.F. Ful lam Inc. , Schenectady, N.Y.

Received September 16,1983; accepted October 11, 1983. 0 1984 ALAN R. LISS, INC

204 C.A. EDWARDS, G.K. WALKER AND J.K. AVERY

D ) Increase t h e c u r r e n t across t h e tungsten wire. As the wire

heats up, t h e Vlctawet may be e jec ted from the basket I f heated too

rap ld l y . I f heated proper ly, t h e Victawet should s t a r t t o melt .

Applytng more c u r r e n t a t t h l s p o i n t w l l l evaporate the we t t l ny agent

over t h e microscope s l l des . Contlnued heat ing f o r twenty t o t h i r t y

seconds should be s u f f l c l e n t t o completely evaporate the Vlctawet.

The s l l d e s a re now ready t o be dlpped I n t h e Formvar so lut ton. Texts Gf

e lec t ron microscopic technlque may be consul ted f o r t h e remalnlng steps whlch

have become r o u t l n e I n near ly every E.M. laboratory . However, consu l t Howard

(1973) or Dawes (1979) for a d e t a l l e d account of Formvar g r l d coat lng

preparat lons.

We have had repeated success w l t h t h l s technlque. Nearly every attempt

t o remove Formvar f l l m from Vlctawet pre- t reated microscope s l l d e s has

r e s u l t e d i n a smooth and very c lean support f l l m .

JhbEmes

Dawes, C.J. (1979) B l o l o g l c a l Techniques for Transmission and Scarininy

E lec t ron Mlcroscopy. Ladd Research Indust r les, Inc.

Howard, K.S. (1983) The preparat on o f formvar g r l d s

e l e c t r o n mlcroscopy. In: E ec t ron Mlcroscopy SOC

B u i l e t l n , Vol. 13, No. 1, pp. 96-98.

f o r t ransmlssion

ety of America

Supported by Grant DE-02731 Nat lonal l n s t l t u t e s o f Health, Bethesda, MD.