Homebrew PCBs

Well I needed to make a board this weekend but did not realize that I
was out of the developer.  I use the M G Chemicals 600 series board
with positive resist.  Normally use the M G Chemicals developer which
is Sodium Hydroxide, but can not get it over the weekend.  Never have
found a place to buy the Sodium Hydroxide without ordering it in.

I tried some Washing Soda but so far it does not seem to do anything
to the resist.  How strong should the washing soda need to be mixed? 
or will the washing soda even work on the M G Chemicals positive resist?

Ben