grainy, crystalline surface using shellac

[patchworkkitten]

Hello all, I am the 'veriest beginner' and don't do any woodworking... but I am trying to use some shellac as a finish.

I have covered an MDF box with fabric that has been glued down and then I brushed on some shellac. The first time I followed the manufacturers instructions and mixed the shellac (it was a tin of premixed white shellac) with some methylated spirits. I used diggers 95% from bunnings. When it dried it was all rough like little crystals all over the surface. I am not sure if it reacted to the glue somehow, or the methylated spirits, or if the tin was too old (it said that it had been manufactured december 2004 but the tin was sealed). I kept the receipt if I need to return the shellac, but I've never used it before so I just don't know.

I tried it on something else without thinning it down and it seemed to have a less crystalline texture but then it went a bit blotchy because it ran down the side a bit and spoiled the finish on the other side, so I think I would prefer to use thinner coats.

Is this grainy crystalline surface normal? If so, how can I make it more smooth? Not sure if I can sand this now as I don't want to sand through and damage my fabric underneath. I would like to learn something from this so that I know what to do in my next (hopefully successful!) fabric-covered-box project.

Thanks in advance for your help

[MacS]

I would return it.

Shellac, is usually intented to be thinned out, its an "evaportive coating" so that you can mix it to whatever "cut" (viscosity) you want to use it out, it will work.

You should try coating some pieces of scrap woods to get the feel to see how the shellac works.

Good Luck.

[Glennet]

I've not used shellac much but have found it very easy to apply and have had good results so far.

It is recommended that you should use pure methylated spirits, not the ordinary variety. My bottle is the Sceney's 100%. It says "for french polishing" on the label.

I use the dry flakes because shellac should be freshly mixed and the flakes seem to last indefinitely. I mix equal volumes of the loose flakes and meths.

[jerryc]

Obviously you want to save the fabric covered box if possible. It's hard to know precisely what is causing the problem as you haven't told us what glue you used on the fabric and it might be reacting with the glue, but that is just a guess.

Since shellac is normally recoverable by more thinning with meth, I would try just a wash with meth on a cloth in as inconspicuous spot on the box as possible and hope this eases the trouble. Sanding should be the last resort.


Jerry

Everyone is entitled to my opinion

[ubeaut]

White shellac has a max shelf life of 2 yrs so yours is just a tat too old. Should have been used by Dec. 2006.

From what I understand you applied the shellac over the material. If this is the case then there will probably be tiny fibres of material which have stood up with the shellac application and when dry will look like minute rain drops or crystals on the surface, which is basically what I would expect to happen.

Cheers - Neil

[jerryc]

Neill,

It's obvious I don't work with fabric and shellac. Didn't think laterally enough to see that the shellac could just have stiffened the fibres of fabric in the same way it does to wood splinters. Never too old to learn and never too proud to admit mistakes

Jerry


Everyone is entitled to my opinion

[astrid]

what sort of fabric is it?
shellac will penetrate cotton, silk, linen and possibly wool, but synthetics?

Astrid

[MacS]

FWIW

Some glues are not effected by shellac, if the glue you used was not completely cured, then the meths could have effected the glue..

What glue did you use?

You might want to also try using Water Clear Acrylics instead of the Shellac.

As always, first start with a completed sample to know if it will work.

[patchworkkitten]

Ah interesting! Perhaps the grainy surface was caused by the wood underneath or the fabric raising like Neil suggests. I gave the surface of the box a light sand anyway to see what would happen, and it didn't damage the fabric at all; it did give a better texture. I called the supplier of the shellac and told him about the date on the can and he agreed that it was too old and in fact he had already complained to the supplier this week and had got a new batch in.

As for what kind of glue I used - I just boiled common white flour with water. Although the glue had dried before I applied the shellac. And as for the type of fabric, just plain craft cotton. I think when I get the new batch of shellac it will dry faster and less sticky so I can put on more coats? Its an interesting project anyway, the shellac gives a nice antique colour