Hello! Im pretty new to soaping but not new to beer so I feel, being a brewer, I may be able to add some helpful info finally.
Alcohol is a broad term. When people talk about beer/wine/spirits and refer to Alcohol they are referring to Ethanol. However, there are many other "alcohols" in these beverages known as Fusel alcohols. The biggest concern is Acetone-the most volitile and Methanol. Both chemicals are volitile and poisonous. There is also ethyl alcohol, isopropyl and other fusels that are pointless to list as most have never heard of them. All of these chemicals are the culprits (in higher doses) that cause hangovers. I have a chemistry backround but without testing I can not say for sure what reaction these chemicals would have with a caustic material like NaOH.
These chemicals all have lower boiling points than water- beginning around 63* C. Ethanol, the good stuff, evaporates at about 78*C. Thus, even a light simmer which is typically considered to occur (depending on altitude) around 200F (~95*C) will cause a complete loss if carried out long enough; which also depends on alcohol levels.
So, to make a long story short...
I would reccomend removing ALL of these chemicals prior to combining with NaOH. The exothermic reaction (heat) caused by the NaOH in solution might be enough to remove these but other chemical reactions may also be taking place. Again, without proper testing I can not say for sure.
Other things to consider and possible helpful facts:
* If working your soap ingredients at room temp some of these chemicals may make their way into your bars. Do you want to bath in nail polish remover or wood alcohol? These chemicals would be very minute in the amount neccesary for making soap, but still...
* "beer" typically has a pH of about 5.1 - whats the pH of soap??? Just throwing out a scientific question here to maybe understand more benifits of beer in soap. distilled water should be around 7-7.5 pH - neutral.
* Any "bubbling" occuring while making your Lye solution is most likely your "alcohols" being evoporated at accelerated rates. THIS IS DANGEROUS!!!! Especially if you are working near open flame. ALL FORMS OF ALCOHOL ARE FLAMMABLE, and in concentration EXPLOSIVE!!!!
Now, before I scare everyone away from using beer to make soap I'll say this, the amount of alcohols present in beer in the typical amount used for home soap-making isnt really high enough to cause an explosion. But when distilling off alcohol I suggest doing so in a well ventilated area free of open flame, included but not limited to cigarettes.
*Beer contains Hops! Humulus Lupilus,, ever heard of NIOXIN shampoo? they use hop oil to promote the thickening of hair.
*Beer also contains whole grain barley and sometimes wheat and oatmeal. All of which are good for you!
*Beer still contains many complex sugars unlike honey and cane sugars. These sugars are closer to starch in complexity.
*If you boil beer it will carmalize these sugars and make the beer darker.
Hope this helps!!! (sorry no spell check, its really late.)
Joe