GUI text doesn't function properly?

while true do
    local text = "Welcome to Forever Build 2014!"
    for i = 1, #text do
    script.Parent.Text = script.Parent.Text..text:sub(i,i)
    wait(.1)
    end
    wait(5)
    local text = "This place last updated on July 12."
    for i = 1, #text do
    script.Parent.Text = script.Parent.Text..text:sub(i,i)
    wait(.1)
    end
    wait(5)
    local text = "Now there are two spawn points! Build on different sides of the map!"
    for i = 1, #text do
    script.Parent.Text = script.Parent.Text..text:sub(i,i)
    wait(.1)
    end
    wait(5)
    local text = "We hope you enjoy your experience! Have fun building!"
    for i = 1, #text do
    script.Parent.Text = script.Parent.Text..text:sub(i,i)
    wait(.1)
    end
    wait(5)
    local text = "Credit for the amazing Build v3.1.0 tool goes to kasuku. His tool makes your building experience possible!"
    for i = 1, #text do
    script.Parent.Text = script.Parent.Text..text:sub(i,i)
    wait(.1)
    end
    wait(5)
end

This script makes text appear in individual letters, like so:

H

He

Hel

Hell

Hello

However, when the wait(5) passes, instead of getting rid of the old text, it builds upon it, like so:

Hello

HelloH

HelloHe

HelloHel

HelloHell

HelloHello

Also, I think the script is a bit inefficient. Any way to fix this?