It is very common for both men and women themselves to judge whether a woman is sexually excited by her level of natural lubrication. It is almost as if lubrication in women is seen as equivalent to an erection in a man. The reasoning is that if a woman is excited, she should be very wet, and that her level of lubrication corresponds exactly to the level of excitement that she is experiencing.
This, however, is not often the case, especially immediately. The first thing to understand is that daily vaginal moisture is different from the lubrication of sexual arousal. The vagina normally has a certain amount of moisture in the tissues, which changes with the monthly hormonal cycle in pre-menopausal women. Some women may even feel more comfortable wearing a panty liner at that time of the month because of the amount of wetness they experience. In post-menopausal women, the vaginal tissues have less moisture because of a lack of estrogen, which supports these tissues.
This moisture is the way for the body to keep the mucosal tissues of the vagina healthy. It is not the same thing as natural lubrication that occurs when you reach a high and prolonged state of sexual excitement and arousal. This lubrication occurs when the glands that surround the opening of the vagina have increased blood flow to the surrounding tissues as a response to sexual arousal. This actually causes moisture to flow from the blood vessels and surrounding spongy tissue into the glands because of increased blood pressure in those tissues.
As this moisture passes into the glands, they release this wonderful natural lubrication. You will notice a distinct difference between this lubrication and the normal moisture of the vagina. This natural lubrication is much slipperier and is mainly produced around the opening of the vagina.
It is slippery enough that it can be spread to the inner vaginal wall as well as over the lips and even up to the clitoris. But the brain being what it is, a person becomes accustomed to a certain set of stimuli — even if those stimuli are exciting. Because of this, the lubrication effect happens more slowly. This does not mean that a woman in not physical or emotionally excited.
Actually, a woman may very easily reach orgasm without having natural lubrication and she will find that she becomes very wet after the orgasm. There is also a great deal of variation between women and the rate and amount that they produce natural lubrication, just as there is great variation in men and their production of pre-cum. Many times couples, and women themselves, get discouraged during foreplay or sex play because they are not getting lubricated quickly. Men often interpret this as the woman not being excited by him or by what they are doing.
Women may start to wonder if there is something wrong with them. Obviously, these negative interpretations can put a big damper on sexual excitement and sexual desire. The trick is to keep the stimulation going so that eventually, the lubrication will start to flow.
Some women prefer to start off with some artificial water-based lube until her own wetness kicks in, and some women find that they can only get properly lubricated if they feel themselves already wet, either with saliva, pre-cum, or artificial lube. Many women do not even feel that they have sexual desire until they have had direct physical stimulation for 5 or 10 minutes, and this may be one contributing factor.
Because of this, it can be very helpful to continue building on sexual excitement and use an alternative lube source as mentioned above to get things started. It is one of the reasons that artificial lube exists and the second best use for saliva.